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ISSN 0250-4162
SCOPUS
Yep
A publication of the Ornithological Sub-Committee of the East Africa Natural History Society
Edited by Graeme Backhurst
Volume 13, No. 1, July 1989
SCOPUS
Cover illustration from a gouache painting by Dr P.A. Clancey
Scopus is normally published three times a year (although issues may be com- bined) by the Ornithological Sub-Committee of the East Africa Natural History Society. Subscriptions are payable to the OSC Hon Treasurer (and Secretary), D.A. Turner [tel 48133], Scopus a/c, Box 48019, Nairobi, Kenya, at the following rates:
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Notes for Contributors
Scopus welcomes original contributions on all aspects of the ornithology of eastern Africa—the area from the Sudan south to Mogambique. Contributions will be assessed by independent referees. The material published is divided into ‘papers’ and ‘short communications’, the latter will usually be less than two pages in length.
Continued inside back cover
Scopus 13: 1-80, July 1989
ECOLOGICAL AND BIOGEOGRAPHICAL ASPECTS OF FOREST BIRD COMMUNITIES IN MALAWI
Francoise Dowsett-Lemaire
SUMMARY Malawi has an extremely varied relief, with many small patches of rain forest (totalling today only 320 km”) scattered at over 40 major sites on hills, mountain scarps and plateaux (Table 1, Fig. 1). Evergreen forests embrace all types from lowland to montane, between 500 and 2450 m, but are most extensive above 1400 or 1500 m.
The breeding avifauna of the forest interior and canopy consists of 105 species of 66 genera; in addition there are 54 marginal species, i.e. non-breeding visitors or residents of the ecotone. From an intensive survey of all major forest localities, information is given on the feeding ecology, distribution, altitudinal range, local densities and movements (if any) of the breeding avifauna (Chapter 6). The 105 species comprise 38 Montane (near) endemics, 14 Eastern endemics and 53 Pluriregional elements (Chapter 5); 67 (64 per cent) are essentially or wholly forest elements in Africa. The most important families are the Pycnonotidae (11 species), Turdidae (13), Sylviidae (10) and Muscicapidae (9). Uy to three congeneric species (in Andropadus, Turdus, Apalis, Nectarinia) or four (Phyllas trephus) coexist locally. The total size of some isolated populations is very small: thus the localized taxa Stactolaema olivacea belcheri, Oriolus chlorocephalus, Turdus fischeri and Apalis chariessa all number less than 100 pairs in their Malawi range. But densities of at least 33 common passerines range from 2-20 pairs/10 ha.
The country has a single rainy season, in the summer months; 86 per cent of 1408 breeding records for 64 species fall in the period September to December, i.e. in the late, hot dry season and at the beginning of the rains (Chapter 7). There is evidence for more than one normal brood per year in only three species.
Most of the montane forest birds occurring in Malawi are widely distributed in the mountains of Africa (Chapter 8). Thirty-five of the 38 species (92 percent) are shared with mountains to the north, and only 18 (47 per cent) with mountains to the south; thus the forests of Malawi (including the southeast) clearly belong to the Tanzania—Malawi regional mountain system of Moreau (1966). As many as 20 species reach their southern, southeastern or southwestern limits of range within the latitudes of Malawi and adjacent N Mozambique. Non-montane species are much less affected by this trend of latitudinal impoverishment.
The forests of south-central Malawi (west of the Rift) are very small and species-poor (56 species), whereas those of the north and southeast are equally rich (over 80 species, 63 in common). The fact that the southeastern forests have a reduced montane component (24 species vs 34 in the north, cf. above) is compensated for by a greater number of lowland elements, especially Eastern endemics (Chapter 9.1). These trends seem related to the better structural development and more diverse flora of the habitat at low and medium altitudes in the southeast, and at submontane levels in the north (Chapter 9.2). Bird species diversity in each of the two main regions of Malawi parallels variations in floristic diversity over the altitudinal gradient, and reaches a peak of 68 species at
2 Francoise Dowsett-Lemaire
1600-2050 m in the north, and 66 at 1200—1400 m in the south (though slightly lower in the cool gorges of Mulanje Mt). The proportion of montane elements varies from 0-10 per cent in lowland forest (SOO—-1100 m) to 21-31 per cent in mid-altitude forest (1000-1100 to 1500—1600 m) and 47-77 per cent in submontane and montane forests. No two species have exactly the same altitudinal range, and there are local variations according to size and exposure of mountains. Within particular forest types and regions (Chapter 9.3), forest area is the environmental factor most consistently correlated to bird species numbers. In the north, structural complexity (expressed by tree species numbers) and altitudinal range are also strongly correlated to bird species diversity, but inter- correlation between these factors and area calls for caution in the interpretation of regression relationships. |
The thrush Alethe choloensis is the only species endemic to Malawi and adjacent N Mozambique (Chapter 10). Isolated populations of some other bird species have under- gone racial differentiation, but not all isolates show phenotypic change.
Local gaps in the distribution of forest birds (Chapter 11) are to a large extent explained by ecological factors—i.e. the size or structure of certain forests is unsuitable. On the other hand, geographical or altitudinal replacements of congeneric species are frequent; interspecific competition in some genera (especially Apalis warblers) may lead to local absences. Isolation combined with historical changes in the extent of forest may explain others.
Very few stenotypic forest birds undertake migratory movements on a large scale; montane species include Columba arquatrix, Schoutedenapus myoptilus and the altitudi- nal migrant Pogonocichla stellata (Chapter 12). Movements to lower altitudes in the non- breeding season have been observed in over 20 species and are especially noticeable down the slopes of Mulanje Mt (the only massif in Malawi with a continuum of forest from montane to lowland levels). In the majority of species, this habit affects only a small proportion of the population and its ecological benefit may be negligible. In addition, erratic and inter-montane movements have been identified in 15 species, involving distances of 20-100 km. Apaloderma vittatum and Malaconotus multicolor in particular show remarkable exploratory behaviour; one Apalis chariessa even crossed the Rift Valley. Clearly some species could respond to local changes in climate and forest cover fairly promptly, but the potential mobility and colonizing ability of others seems very limited.
It is as yet very unclear to what extent forest cover in the African mountains was affected by the climatic changes of the late Quaternary (Chapter 13). But everywhere in Malawi there is ample evidence that upland forest has receded under the influence of bush- fires for many centuries. From biogeographical data, the most ancient forest sites are probably in the Mulanje—Thyolo area in the south, and on the Nyika and N Viphya Plateaux in the north. The Misuku Hills in the extreme north, although floristically the most diverse forests in the country, appear incompletely recolonized by forest birds.
Ecology and biogeography of forest bird communities in Malawi 3
CONTENTS 1. Introduction 3 2. Description of the forests 8 2.1. Forest zonation | 8 2.2. Recent changes in forest cover and conservation status 9 2.3. Fragmentation and isolation 9 2.4. Structural features 10 3. Climate 11 4. Exploration of the forests 12 4.1. Vocal activity of forest birds 12 4.2. Field coverage 12 5. Biogeographical elements 13 6. Ecology, distribution and movements of forest birds 15 7. Breeding seasons 48 8. Biogeographical position of the mountains of Malawi 54 9. Regional and altitudinal variations in numbers and composition of species 57 9.1. Variations between regions (North, Centre, Southeast) 57 9.2. Variations along the altitudinal gradient 59 9.3. Area and other factors related to species numbers 61 10. Endemism and isolation in the highlands of Malawi 63 11. Distribution gaps and the role of competition and isolation 65 12. The mobility of forest birds 67 12.1. Intra-African migration 67 12.2. Altitudinal migration 68 12.3. Nomadism and inter-montane movements 70 13. Late Quaternary history of climate and vegetation in the African mountains 71 Acknowledgements 72 References 73 Appendices 78
Chapter 1. INTRODUCTION
With a land area of 94 276 km? Malawi is a relatively small country by African standards. Situated more or less half-way along the chain of mountains that extends from Ethiopia to South Africa, it has a biogeographical position of considerable interest; the depression of Lake Malawi, 540 km long from north to south, and of the Shire River which drains the Lake into the Lower Zambezi, forms the southern end of the Great African Rift. From the valley floor of the Lower Shire (50—100 m alt.) to the high mountain peaks of Nyika (2607 m) in the north and Mulanje (3002 m) in the southeast, the varied land configuration has produced a great diversity of woodland and forest types.
With the exception of a narrow band along the shore of Lake Malawi, most of the land north of 14°30S lies at 1000-1100 m, above which isolated hills and several high plateaux rise to 1500-2600 m. South of the Lake, the peneplain lies lower (500-600 m) and highland areas are much less extensive but rather more prominent (Fig. 1). The main vegetation type at 500-1500 m is ‘miombo’ woodland (dominated by several species of the Caesalpiniaceae Brachystegia and Julbernardia), with local pockets of ‘mopane’ Colophospermum mopane woodland, Acacia—Combretum savanna and thickets. The valley of the Lower Shire was covered with dense thickets, deciduous Sterculia forest and
Continued on p. 6
4 Francoise Dowsett-Lemaire
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Fig. 1. Map of Malawi north of 13°30S
Ecology and biogeography of forest bird communities in Malawi 5
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Fig. 1 continued. Map of Malawi south of 13°30S
6 Francoise Dowsett-Lemaire
Acacia savanna now largely cleared for cultivation, except in protected areas such as Lengwe National Park. Rain forests—i.e. excluding evergreen forest lining streams—are rather localized at altitudes of 500 to 1100 m. Between 1000/1200 and 1600 m, rain- exposed sides of large mountains and several small hills bear patches of transitional, mid- altitude rain forest, but the most extensive areas of evergreen forest are found above 1400 or 1500 m. The total area of forest today (excluding riparian vegetation) is near 320 km7?, with almost 70 per cent of this above 1600 m, and it is fragmented in over 40 major sites on hills and plateaux (Table 1). Most of the Mid-Tertiary surface is underlain by rocks of pre-Cambrian age (Chapman & White 1970); there are no centres of volcanic activity within Malawi, although that of Rungwe Mt in SW Tanzania is only 50 km north of the international border.
Relative to the small size and isolation of forest fragments, the avifauna is strikingly diverse. Bird collection in the country started in the late nineteenth century, but the forest avifauna remained poorly known until the 1930s and 1940s when C.W. Benson visited a large proportion of the forests (Dowsett 1981). His work culminated in the production of an annotated check-list (Benson & Benson 1977), which summarizes information on distribution and breeding of species from a great many scattered publications. This initial set of data proved invaluable in planning further studies in distribution, coupled with investigation into the ecological niche of individual species and the status of localized, potentially endangered forms. In a first phase of our research, the ecology and population dynamics of the breeding avifauna of the Nyika Plateau—the largest montane complex in the country—were studied for two-and-a-half years (Dowsett-Lemaire 1983a, 1983c, 1985a, Dowsett 1985, Dowsett & Dowsett-Lemaire 1984, 1986). Characteristic features of these montane forest birds appeared to be a marked breeding seasonality, high survival rates and site-fidelity, and low breeding productivity. Hence adaptation to habitat change seems likely to be slow.
The status and numbers of forest birds elsewhere in the country were then assessed over a period of 17 months, when all major forest localities were surveyed. Several important forest sites have become greatly threatened by increasing human activities; others were explored for the first time. It also appeared that Benson’s accounts of the places he visited had often been selective or incomplete—e.g. he recorded only 18 species from the N. Viphya forests now known to have at least 52.
The present paper describes the distribution, ecology and local densities of 105 species of the forest interior and canopy, while 54 marginal species are more briefly mentioned. Over 1400 breeding records show the egg-laying season of 64 species. The biogeographical position of the Malawi mountains is placed in its African context, while regional variations in species numbers are analysed in relation to the altitudinal gradient, structure, size and floristic diversity of forest isolates. The possible role of interspecific competition and isolation in shaping the mosaic-like distribution of some forest birds is discussed. Special attention was paid to the timing and extent of migratory movements undertaken by a few montane species. As breeding status and distribution became accurately known, it was possible to identify erratic and inter-montane movements in 15 species. Evidence for the mobility of montane forest birds in Africa is reviewed. Finally, the controversial theories on the late Quaternary history of climate and vegetation in the mountains of eastern Africa are critically examined. Based on biogeographical data, some hypotheses are presented on the relative age of different forest areas in Malawi and on likely routes of recolonization of certain forest sites.
Bird nomenclature follows Dowsett & Forbes-Watson (in press) except for the
Continued on p. 8
Ecology and biogeography of forest bird communities in Malawi
Table 1. Main features of the major localities of rain forest in Malawi Forest size was measured from aerial photographs, altitude with a calibrated altimeter
Locality
North of 14°S
Misuku Hills: Mugesse Matipa-Wilindi
Mafinga Mts
Jembya Plateau
Musisi Hill
Nyika Plateau: southwest slopes* central plateau? eastern scarp elsewhere (S, SE)
North Viphya Plateau: Uzumara Chimaliro Choma
Kaningina Hills
South Viphya Plateau: Nthungwa Chamambo Kawandama central plateau? eastern scarp?
Northern Lake-shore:
Kalwe (Nkhata Bay)
Nkuwadzi Mzuma Kuwilwe Hill Chipata Mt Ntchisi Mt
Altitude (m)
1600-1880 1700-2050 1600-1800 1850-1920 1600-1850
1925-2225 2250-2450 1750-2350 2000—2200
1600-1920 1850-2000 1750 1000—1500
1600—1800 1600-1800 1750-1850 1600-1850 1100-1500
500 600 600—700 500-1200 1400-1550 1350-1450 1450-1640
Forest type
submontane submontane submontane submontane submontane
submontane montane
submontane submontane
submontane submontane submontane mid-altitude
submontane submontane submontane submontane mid-altitude
lowland lowland lowland lowland mid-altitude mid-altitude submontane
South of 14°S, west of Rift
Dzalanyama Range Chongoni Mt Mlunduni Mt Dedza Mt?
Chirobwe Mt
Kirk Range: Mvai Mt Dzonze Mt
Dzonze Khaya forest
Chimbia Hill
Nsambi graveyards Thambani Hill Malawi Hills
1500—1600 1600-1950 1800—2000 1800-2050 2050-2150 1800-2000
1700-1800 1600-1800 1450 1750-1800 1250-1350 1100-1200 600-940
mid-altitude submontane submontane submontane montane
submontane
submontane submontane mid-altitude submontane mid-altitude lowland
lowland
7 Size (ha) of total (largest area patch) 720 (720) 2400 (1350) c. 250 (44) 160 (133) 300 (114) 550 (90) 2000-3000 (8) 3400 (1300) 72 (19) 540 (520) 180 (106) HS (725) c. 670 (130) 108 (108) 263 (263) bs (51) 2000-2500 (20) c. 2500 (>150) 80 (80) 600 (600) c. 600 (600) c. 200 ? 44 (44) 30 223 (293) 75 (33) Wig! (44) 5 (25) \ 230. ~—«(114) 614 (614) 33 (13) 66 (30) 12 (12) 11 (5.5) 21 (7) 78 (42) c. 400 (400)
8 Francoise Dowsett-Lemaire
Table 1 contd. Size (ha) of total (largest Locality Altitude (m) Forest type area patch) South of 14°S, east of Rift Namizimu Hills 1500-1700 ~ submontane 40 (32) Mangochi Mt 1550-1700 submontane 230 (116) Chikala Hill 1300-1600 mid-altitude 285 (285) Shire Highlands: Malosa Mt 1700-1950 submontane 730 (196) Zomba Mt 1600-1950 submontane 600 (150) Chiradzulu Mt 1450-1750 submontane 150 (130) Lisau Saddle (Chiradzulu) 1300-1450 mid-altitude 160 (160) Ndirande Mt 1400-1600 mid-altitude 60 (60) Soche Mt® 1300-1520 mid-altitude 150 (150) Bangwe Hill® 1350-1550 mid-altitude 60 (60) Malabvi Hill*® 1200-1440 mid-altitude c:30 (30) Thyolo Mt® 1170-1450 mid-altitude 1000 (1000) Thyolo tea estates 1000—1100 lowland 600 (120) Mulanje Mt: foothills® 600-950 lowland c. 200 ? middle slopes*® 900—1500 mid-altitude 1800 (800) upper slopes and plateaux?1500-1850 submontane 1850-2300 montane } 5000 (2000)
* Including 210 ha on the Zambian side.
> Total sizes of forest patches were extrapolated from measurements on a limited number of aerial photographs.
© Excluding 245 ha on the Mozambique side (not visited).
4 Limits between submontane and montane forests cannot be distinguished on photos, and total sizes are lumped.
© Sizes of untouched forest are below those indicated as damaged understorey is not seen on photos; figures are valid for 1982 but still decreasing.
Zoothera thrushes which I prefer to keep in the broad genus Turdus—for their similar features of ecology and behaviour, and Turdus fischeri, morphologically intermediate between Turdus and Zoothera, has typical Turdus feeding habits. Taxonomic changes adopted since the reference works of Benson et al. (1971), Hall & Moreau (1970) and Snow (1978) have largely been explained in Dowsett & Dowsett-Lemaire (1980), also Dowsett-Lemaire & Dowsett (1988a: Tauraco species). Justifications for the more recent splitting of Andropadus nigriceps from A. tephrolaemus, and for the geographical limit between Batis mixta and B. capensis, and some other comments are given in Appendix 1. English names appear once, in the species’ accounts (Chapter 6).
A gazetteer of all forest and other localities not mentioned in Benson & Benson (1977) is also presented in Appendix 2.
Chapter 2. DESCRIPTION OF THE FORESTS
2.1. Forest zonation From their floristic features, three main categories of rain forest can be recognized in Malawi: lowland (with 0-25 per cent montane elements), transitional or mid-altitude
Ecology and biogeography of forest bird communities in Malawi 9
(25-50 per cent montane elements) and Afromontane (over 50 per cent montane elements) (Dowsett-Lemaire 1988a, 1989b). Within the Afromontane category, montane forests replace submontane above certain altitudes; they are characterized by a marked impoverishment in their floristic composition and certain structural features, such as low canopy and abundance of non-vascular epiphytes. Montane forests sensu stricto occur only on the highest mountains, i.e. on the Nyika Plateau (above 2250 m), Dedza Mt (above 2050 m) and Mulanje Mt (above c. 1850 m).
2.2. Recent changes in forest cover and conservation status
Early this century large areas of lowland forest were cleared around Thyolo and Mulanje with the establishment of farming estates. Similarly most of the lowland forest of the northern Lake-shore (near Nkhata Bay) gave way to tea and rubber plantations. Else- where, as in the Misuku Hills (on the Tanzanian border), and central Malawi (e.g. between Dedza and the Kirk Range), human population was already dense before the turn of the century, and all that remains of mid-altitude forest is in the form of graveyard relicts. Afromontane forests have suffered least from direct destruction, but dry season bush-fires have taken their toll over many centuries. Some of the montane grassland and secondary growth on high plateaux such as the Nyika and South Viphya is clearly derived from forest (Dowsett-Lemaire 1985b: 363-6; also Chapter 2.4).
Most of the surviving evergreen forests were incorporated into reserves from the 1920s, and the Nyika forests are in a national park. Exceptions include the remnants of fine lowland forest scattered on the tea estates near Thyolo; some are well protected, but one of them, on Nanzadi Estate (now Nansadi), was totally destroyed in the 1960s (Chapman & White 1970: 155, 160). The small forest on Mpingwe Hill near Blantyre is now reduced to a few trees and that on Machemba Hill north of Mulanje is being felled for fire-wood.
Overall, forest reserves have received adequate protection, though fires remain a problem in places (e.g. eastern foothills of the Nyika, Mulanje). Except very locally, especially the Widdringtonia forests on the Mulanje plateaux, they were not exploited for timber. In the last 25 years however, increasing human population in the south of the country has posed a serious threat to the survival of mid-altitude forest (Dowsett-Lemaire & Dowsett 1988b): over 15 km? have been lost to garden encroachment on the S-SE slopes of Mulanje Mt, and about 5 km? all around Thyolo Mt (the total forest area thus decreasing from 15 to 10 km’). Felling for fire-wood is also damaging the hill forests near Blantyre, especially Soche and Bangwe. In central Malawi, the largest forest remnant, on Chirobwe Mt, suffers from illegal felling of understorey trees.
2.3. Fragmentation and isolation
Most forest isolates in Malawi are of strikingly small size; in addition, there is much fragmentation of the forest habitat in about half of the 50 or so localities mentioned in Table 1: an indication of this is given by the size of the largest patch of forest for each site. Single blocks of forest in excess of 500 ha are to be found in only seven localities: Misuku, E Nyika, N Viphya (Uzumara), N Lake-shore, Chirobwe, Mulanje and Thyolo.
On the Nyika, montane conditions prevail above 1800 m, and of the 1800 km? at 1800—2600 m, forest cover (c. 65 km’) represents less than 4 per cent. On two other large plateaux, the North Viphya (c. 400 km? above 1600 m) and South Viphya (820 km? above 1600 m), it is of the same order, near 2 and 3 per cent respectively. By contrast, forest on the Malosa and Zomba plateaux (c. 50 km? above 1600 m) covers about a quarter of the total area, and on the Mulanje plateaux (200 km? above 1800 m) near one sixth. Mulanje
10 Francoise Dowsett-Lemaire
Mt receives more rainfall than any other massif in Malawi (Chapter 3) and is also unique in having a continuum of forest from lowland to montane levels on the southern and southeast slopes. Chisongeli Forest (900-2000 m, southeast Mulanje) still measured some 38 km? in 1974 although deforestation was well under way, and was the largest single block of forest in the country. Today, little forest remains below 1500 m, and the main patch of mid-altitude forest is in Ruo Gorge on the southern slopes (600 ha from 900 to 1800 m).
The most isolated forests in the country are on Chipata and Ntchisi Mts, separated by c. 100 km of woodland and cultivation from the S Viphya to the north, and from Chongoni- Dedza to the south (Fig. 1). Distances between forested highlands on either side of the Rift Valley (Kirk Range to the west, Zomba-Malosa to the east) are 70-80 km; the Dzalanyama Range is similarly isolated from Dedza and Chongoni Mts, Mangochi Mt from Chikala Hill, and the Malawi Hills from the Thyolo scarp and Chiperone Mt in adjacent Mozambique. All other forest sites are within 20-50 km of each other.
The chain of Tanzanian mountains starts only some 20 km north of the Misuku Hills, at Isoko, and the large Rungwe massif is 50 km distant. The most important forested mountain of northern Mozambique, Namuli, is 150 km ENE of Mulanje. But the highlands of eastern Zimbabwe and southern Mozambique are more distant, starting some 300 km SW of the Mulanje and Thyolo scarp, on the other side of the Zambezi plains; the Malawi Hills are 200 km north of Gorongoza Mt (the shortest distance between any two forests across the Zambezi) but have lowland forest only.
2.4. Structural features
The floristic composition and physiognomy of the forests have been described in detail in Dowsett-Lemaire (1985b, 1988a, 1989b, in press), but some structural features relevant to bird distribution are mentioned here. North of 14°S, the most mature and luxuriant forests are at submontane levels (especially Misuku, Nyika, N Viphya, Nthungwa on S Viphya, Ntchisi): these have a tall canopy (25-30 m, locally 40 m as in Mugesse) and 2-4 species of giant trees emerge to 35-45 m. Medium-sized trees (8—18 m) do not form a distinct stratum, but the lower storey does (4—8 m), and in the wetter forests (Misuku, E Nyika, Uzumara) it is practically impenetrable, with extensive thickets of Acanthaceae and Dracaena. Lianes are numerous, and edges of forest and clearings are often draped in walls of leaves. Fig trees of several species are prominent at Ntchisi, and in the Misuku Hills below 1900 m.
Climate, exposure and other factors are less favourable to the development of mature forest elsewhere. At Jembya, the canopy is still 25-30 m tall and fairly closed, but the understorey of this small patch (exposed on top of a flat plateau) is rather open. The forest patches on the eastern slopes of the Mafinga Mts have a somewhat broken canopy (20-25 m) and no emergents; those on Musisi Hill are taller (25—30 m, with some giant trees) but the canopy is interrupted by several big fire-induced gaps. Most of the S Viphya Plateau bears numerous scars of past fire damage: 80 per cent of the forest area at Chamambo, on the eastern edge of the plateau, is clothed in a secondary 18 m-tall Bridelia—Macaranga association, with tall forest restricted to the main stream gullies. At Kawandama, on an even more exposed southeast extension, the forest is smaller, more fragmented, with big fire-induced openings. Charred stumps of Ocotea usambarensis (a forest interior tree) are scattered in short grassland up to 200 m from the forest edge.
The small patches of montane forest on the central Nyika decrease in height (15 to 8 m) with increasing altitude (2250 to 2450 m), and no more than a few stunted trees grow at 2500 m, near the grassy peak (2607 m).
Ecology and biogeography of forest bird communities in Malawi 11
In contrast to submontane forests, mid-altitude forests in the north are rather localized and, with one or two exceptions (especially Ntchisi), are more fragmented and secondary in structure and species composition. The two most important areas (Kaningina, E Viphya) are locally connected by riverine forest to the Lake-shore, where a few blocks of once extensive lowland forest have been preserved. Away from streams, the canopy of these forests is dominated by two species of briefly deciduous Brachystegia trees (including flat-topped B. microphylla), 30-40 m tall, and widely scattered. Numerous lianes entangle the larger trees to the mid-stratum (10-18 m tall), and much moisture exudes from the understorey, often rendered impenetrable by thickets of woody creepers and shrubs.
South of 14°S submontane forests are considerably impoverished both structurally and in tree species composition (with a total of 150 species of trees and woody shrubs 2 m high and above, against more than 236 in the north). The canopy is usually less than 18 m high, fairly discontinuous, and with no emergents. Little pockets of taller forest (20-25 m) are found in a few places: on the eastern side of Chirobwe Mt (less than 50 ha), Mangochi Mt (less than 30 ha) and on some upper slopes of Mulanje Mt (at 1600 to 1900 m), where Olea capensis and Widdringtonia cedars emerge to 25—30 m. As on the Nyika, the height of montane forests on Mulanje decreases with altitude, and the upper limit of dwarf forest is near 2300 m.
By far the most luxuriant forests in the south are at medium altitudes: those on Chikala Hill and the southern slopes of Mulanje are among the finest in the country. They are dominated by flat-topped Newtonia buchananii which forms an upper canopy at 30-40 m. The forest on Thyolo Mt is also rather lush and moist, with three species of strangling Ficus as the dominant large trees. Soche and Bangwe Hills had some well-developed rain forest, now severely encroached upon. The forest on Lisau Saddle (in the rain shadow of Chiradzulu Mt) is 30 m tall but noticeably drier, with briefly deciduous canopy trees (flat- topped Albizia, Celtis, etc.) and a rather open understorey.
The structural features of the lowland forests in the south (foothills of Mulanje and Thyolo, Malawi Hills) differ strikingly from those of the Lake-shore forests in the north. The canopy is made up of many more tree species of which the crowns are usually contiguous, and the understorey is less dense and moist.
The substrate of the southern forests at all altitudes is more rocky than in the north, and holds less surface water.
Chapter 3. CLIMATE
The single rainy season lasts from November to March or April, during the austral summer, when temperatures remain fairly constant. It is followed by a cold dry season, with a drop of several degrees Celsius in May—August; spells of mist and occasional showers are then not infrequent on most mountains, hills and east-facing escarpments. Temperatures and drought increase from mid-August to October, October and November being the hottest months. Overall, the summer rains start and finish 2—3 weeks later in the north than in the south, and in the extreme north (e.g. Misuku) rainfall is still significant in May.
Mean temperatures vary monthly from 20—21°C to 24—25°C on the edge of lowland forest at 500-700 m (Lake-shore, Malawi Hills); from 13-16°C to 20—23°C at 1000-1400 m (e.g. Mzuzu, Shire Highlands); and gradually drop with increasing altitude, to reach 10—11°C in the coldest months (June-July) and 15—17°C in October-November
12 Francoise Dowsett-Lemaire
on the high plateaux of Nyika and Mulanje above 2000 m. Night frosts occur occasionally on most highlands from 1800—1900 m between May and August: on the Nyika the annual average of frosts remains low (seven nights at 2300 m) but is rather higher on Mulanje.
Mean annual rainfall is known from the following forest localities: Nkhata Bay (1700 mm at 500 m); Malawi Hills (1500 mm at 750 m); near Misuku (1450 mm at 1450 m, below the level of the forests); the Nyika Plateau (where it varies from 1000—1200 mm on the central plateau, at 2250—2500 m, to c. 1700 mm on the top of the eastern escarpment); the S Viphya Plateau (e.g. 1310 mm near Chikangawa, 1750 m); Zomba Mt (2200 mm at 1830 m); and Mulanje Mt (2400-3100 mm above 1900 m, also over 2400 mm on the southern slopes). A small proportion of this falls in the ‘dry’ season, usually 6—8 per cent, but more on Mulanje (17-21 per cent), the Thyolo area (14 per cent of 1327 mm for Thyolo town), the Malawi Hills (17 per cent) and the Nkhata Bay Lake- shore (19 per cent). The southwest Nyika, though relatively well forested, may be exceptional in being totally dry for the best part of six months, between May and October (Dowsett-Lemaire 1985b).
Chapter 4. EXPLORATION OF THE FORESTS
4.1. Vocal activity of forest birds
Overall, the best time to census territorial birds is from late August to December when vocal activity is at its peak, and no later than February—March when several breeding migrants terminate their stay.
In the majority of species, full song is heard in all months of the year, but less frequently outside the breeding season (Chapter 7)—Tauraco spp, Apaloderma vittatum, Pogoniulus spp., Stactolaema spp., Alcippe, Andropadus nigriceps, Phyllastrephus flavostriatus, Cossypha anomala, Bradypterus spp., Apalis spp., Batis spp., Elminia, Laniarius spp., Malaconotus spp. In several of these, adults are mated for life (Dowsett 1985) and contact is maintained by frequent vocal signals. In a few species full song is interrupted for a period from the end of breeding, particularly when moulting, but call- notes still make them easily detectable: Phylloscopus ruficapilla sings mostly from September to November, and Phyllastrephus placidus in the rains; Sheppardia sharpei and Onychognathus walleri resume song in March—April after an interruption of 3-4 months, and Nectarinia mediocris stop singing for no more than a few weeks at the end of the dry season. Pogonocichla stellata and Sheppardia gunningi produce a subsong in winter.
By contrast, the following become (almost) totally silent for six months or more each year: the rail Sarothrura elegans and some cuckoos (heard in the rains only, but of uncertain resident status), Turdus spp., Alethe spp., the ground doves Turtur tympanistria and Aplopelia larvata. On the Nyika, Turtur is rarely heard outside August—October, but may be vocal at other times elsewhere; Aplopelia is active mostly from October to January. The majority of Turdus olivaceus stop singing in December, and T. gurneyi in January, though some may be heard occasionally until the end of the rains (in May in the north). Alethe spp. are very quiet throughout the dry season until September or October (Dowsett-Lemaire 1987).
4.2. Field coverage Field work in the forests north of 14°S (other than on the Nyika) covered a period of nine months between September 1982 and July 1983, and a couple of weeks in late 1986,
Ecology and biogeography of forest bird communities in Malawi W)
although visits to the Lake-shore and Ntchisi started in 1980. Seven months (between July 1983 and June 1984) were spent in the forests to the south. All forests were explored at least once in the critical period of late August to January, except Musisi in the north (inaccessible in the rains, visited in June) and Dzalanyama in the south (seen in March and June). Overall, the duration of visits was proportional to the size of the forests—for instance, a total of 24 days was spent in the extensive Misuku forests, at two seasons (September—October, February—March), but small patches in the Kirk Range received single-day visits (in November). In relation to size or altitude, the following localities are considered insufficiently prospected: the central part of Matipa Forest in the Misukus (a block of 13.5 km?) was not reached; Kuwilwe on the Lake-shore was visited once (December) from 500 to 700 m (but strips of forest ascend to c. 1200 m); the northern side of Mulanje Mt, including the outlying Mchese Mt, was not seen. The exploration of the forests on Mulanje was concentrated in the areas with the largest remnants: on the southeast slopes (to 1800 m), southern slopes (to 1300 m in Ruo Gorge) and Lichenya Plateau (for details, see Dowsett-Lemaire 1988a).
Apart from the northern side of Mulanje, the only major forest locality (i.e. with more than 30 ha) in the country that remains unexplored is Mauze Hill (1363 m) on the Mozambique border. The patch of mid-altitude forest, partly in Mozambique, was never protected and shrank from 400 to 200 ha in the 1970s; it was never visited by a zoologist.
Outside the Nyika studies, mist-netting was carried out only in Matipa Forest (western side, October); Kalwe (Lake-shore) where 200 m of net lines were operated for a few days in January, April and June; and irregularly at the foot of Mulanje (Esperanza). Voices of most species were tape-recorded; tape playback as well as ‘squeaking’ (a noise mouthed by the observer, imitating birds’ distress calls) were frequently used to elicit response of elusive species. Estimations of bird densities are based essentially on territorial songs located in areas of forest measured from aerial photographs.
From the mid-1970s, there was renewed interest in the avifauna shown by expatriates based mostly in southern and central Malawi. Reliable sight-records of forest birds have been used here, when additional to my observations; names of regular observers are abbreviated in the text as follows: JDA (J.D. Atkins), MGD (M.G. Douglas), NDH (N.D. Hunter), NJS (N. Johnston-Stewart). Johnston-Stewart (1984) published locally on the distribution of forest birds in southern Malawi: unfortunately, his account contains a surprising number of errors of fact and interpretation and cannot be utilized here. Many of my own observations were made in conjunction with R.J. Dowsett.
Chapter 5. BBIOGEOGRAPHICAL ELEMENTS
Moreau (1966), in his major work on the biogeography of the African bird faunas, distinguished mainly between forest and non-forest communities, and within forest, between montane and lowland elements. Though he discussed regional patterns of species richness, and attempted to compare them, he did not publish lists of species to support his arguments, nor did he present a firm zoogeographical framework. One problem was the lack of an accurate map and description of vegetation types on the continent, and this has recently been remedied by White’s (1983a) major work. White divided the African flora into 18 geographically exclusive regional centres of endemism and transition zones. These phytochoria, especially the centres of endemism, are usually characterized by one main vegetation type, i.e. there is concordance of chorology and physiognomy. Malawi lies within two main centres of endemism, and a third one which is a
14 Francoise Dowsett-Lemaire
composite area: 1) the Zambezian Region (sensu White 1983a, also called “Southern Woodland Zone’ by mammologists such as Ansell (1978)), whose most characteristic and widespread vegetation type is Brachystegia-dominated woodland (or ‘miombo’); 2) the Afromontane Region, an archipelago-like region of high endemism in plants (White 1978, 1983a), butterflies (Carcasson 1964), birds (Moreau 1966, Dowsett 1986), but of much more limited endemism in mammals (e.g. Kingdon 1971), the two main vegetation formations being evergreen forest and grassland; 3) the Eastern Forest Region. Phytogeo- graphically, the latter is a composite area extending on the eastern side of Africa from Ethiopia to the Eastern Cape of South Africa; it encompasses the coastal forests of East and southeast Africa, and forest outliers in the Lake Victoria, Somalia—Masai Region and eastern half of the Zambezian Region (west to about 28°E: Dowsett-Lemaire 1988a: 83). The Eastern Forest Region has been given much the same geographical limits by mammologists (e.g. Grubb 1983).
Many bird species are habitat-tied, and a preliminary investigation reveals great similarities between phytochoria and zoochoria. Pending a review of zoogeographical regions in the light of White’s work, the following elements can be recognized for present purposes.
1. Montane (or Afromontane) endemic element: a species limited in its range to the Afromontane Region. The lower altitudinal breeding limit of montane forest birds varies with species but is often 1200-1600 m in central Africa (e.g. Itombwe massif in Zaire: Prigogine (1978); northern Malawi: this study). It is noticeably lower on mountains influenced by cool oceanic currents (thus nearer 600-1000 m on Mt Cameroun: Stuart (1986); and (500) 900-1200 m on the Usambara and Uluguru Mts in eastern Tanzania: Stuart & Jensen (1981, 1985)), and decreases with increasing latitude, to approach sea level in the Cape Province of South Africa. Examples include Apaloderma vittatum, Pogonocichla stellata.
2. Montane near-endemic element: a species predominantly montane, but also resident in small forest outliers at intermediate elevations. Typical examples are Aplopelia larvata and Apalis cinerea, both of which are found locally away from mountains, in mid-altitude forest on the Zambezi—Zaire watershed and some other upland areas. Also a species essentially confined to mountains, but with a wide altitudinal range including locally the foothills (e.g. Coracina caesia).
3. Eastern endemic element: a species confined to the Eastern Forest Region. All are characteristic members of lowland forest communities, though some may transgress into other habitats (e.g. Tauraco spp.), and may ascend the mountains, to medium (e.g. Oriolus chlorocephalus) or high levels (e.g. Bycanistes brevis, which has one of the widest altitudinal ranges, from 0 to 2600 m). The ecology of Cercococcyx montanus varies with latitude, this cuckoo inhabiting lowland forest and thicket between 10 and 20°S, but mostly montane forest north to the equator.
4. Pluriregional element: a species present in two or more of White’s phytochoria. Many occur in forest (secondary and/or primary formations) of the Guineo—Congolian Region (e.g. Stephanoaetus coronatus, Dicrurus ludwigii, Andropadus virens, Malaconotus multicolor, Nectarinia olivacea), while others have a Zambezian plus Eastern distribution (e.g. Tauraco schalowi, Phyllastrephus cerviniventris), or a wider, circum-Congo distri-
Ecology and biogeography of forest bird communities in Malawi 15
bution (e.g. Campethera abingoni, Cossypha heuglini, Apalis flavida, Cinnyricinclus leucogaster); the latter category consists of species more frequent in wooded vegetation other than rain forest.
Species commonly occurring in more than one vegetation type could be termed ecological transgressors—an expression so far used by phytogeographers only.
Chapter 6. ECOLOGY, DISTRIBUTION AND MOVEMENTS OF FOREST BIRDS
The distribution of forest birds in the country is shown in the form of tables (Tables 2, 3, 4, one for each natural region of Malawi) and these are referred to at the beginning of each account. The text for each species gives the biogeographical element it belongs to, describes feeding niche, degree of abundance or exact densities where known (some of the forest stenotypic elements and endangered forms received more attention than others in this respect), other habitat types occupied where relevant, altitudinal range in the breeding season, and movements where known.
A total of 37 non passerines and 68 passerines are found in the canopy and/or interior of rain forest; 67 species (64 per cent) are essentially or wholly forest elements in Africa. The 38 Montane (near-) endemics are all typical forest birds, but four of them are also encountered in tall secondary growth (Chloropeta similis, two Apalis spp., Laniarius fuelleborni) and one (Turdus olivaceus) has adapted to plantations, gardens and dry forest locally, outside Malawi. Most of the 14 Eastern endemics are (essentially) forest elements, but three (Tauraco spp., Cercococcyx montanus) are frequent in other habitats. Of 53 Pluriregional species, 21 are characteristic of primary or secondary formations of Guineo-Congolian rain forest (they are indicated by (GC) below), and a few others are also mainly forest elements (e.g. Phyllastrephus cerviniventris, Ploceus bicolor).
In addition, brief mention is made of 54 marginal species, either non-breeding visitors to forest, species nesting in forest but hunting outside (raptors) or present at the ecotone forest-woodland or forest-grassland. The distribution of the montane elements among these is given in Appendix 3, as it is relevant to some biogeographical trends discussed in Chapter 8.
ACCIPITRIDAE
Five species belonging to four genera hunt, at least part of the time, inside forest; of these, three (Accipiter tachiro, Buteo, Stephanoaetus) have noisy territorial displays (Stepha- noaetus in all months of the year) and are easily detected. By contrast, A. melanoleucus is usually silent and has certainly been under-recorded—its distribution is not tabulated.
Black Goshawk Accipiter melanoleucus. Pluriregional (GC). Nests from forest are known from Misuku, Nyika, Ntchisi, Chiradzulu, Thyolo Mt, Malawi Hills, but more often seen in open country and woodland (also Pinus and Eucalyptus plantations) than in forest. 50-2300 m.
African Goshawk Accipiter tachiro. Pluriregional. Tables 2, 3, 4. Hunts small mammals and birds in forest understorey (seen snatching a Phyllastrephus flavostriatus off a trunk) as well as outside. Widespread, but in some areas more common in miombo woodland than forest—as on N Lake-shore where forest may be too dense for easy hunting—or in
Continued on p. 21
Francoise Dowsett-Lemaire
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Ecology and biogeography of forest bird communities in Malawi
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Ecology and biogeography of forest bird communities in Malawi
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20 _ Francoise Dowsett-Lemaire
Table 3. Bird species proven or likely to breed in the following rain forests of south- central Malawi submontane and montane (Chongoni to Chimbia, 1600-2150 m), mid-altitude (Dzalanyama, Kirk Range relicts, 1250-1600 m) and lowland (Thambani, 1100-1200 m). Symbols as in Table 2.
Kirk Range.
ss}
= om = oO ei
Sn) esi ial 3 o Me
S| om sd 3 eo chk N we) a 2
an5 8.3. §. 38. Sooo
N ra) o ta cs N < . es Bird species a O S QA O = (as O g on Accipiter tachiro (P) 5 x x p a OA ee SAT x Stephanoaetus coronatus (P) x x ; : ; : x Sarothrura elegans’ (P) ; (0) Columba arquatrix (M) (x) x : Xx : Turtur tympanistria (P) x x X X x X x x x x Aplopelia larvata (M) X x : x x x x ; x x Tauraco porphryreolophus (E) ; : : } ; : ; , : X T. schalowi (P) x x x x x x x x x , Chrysococcyx cupreus (P) (x) Yes , 4 : x ; ‘ a RNG Strix woodfordii* (P) ; x : x ; : x : x x Apaloderma narina (P) P ‘ é : A i : E x A. vittatum (M) d : i ‘ x : Tockus alboterminatus (P) x ‘ ‘ : , Z ; i ; x Bycanistes brevis (E) (x) ; : : x (v) (vy) W@W) : x Pogoniulus leucomystax (M) § x x x x x x Waa : Indicator minor (P) : ; , x 4 I. variegatus (P) X X ; : ; : 4 : Campethera abingoni (P) x 3 i j 3 x x x Dendropicos fuscescens (P) A x : XG ‘ x x x Smithornis capensis (P) : B : 4 ; i ; : x x Oriolus larvatus (P) s ; 5 ‘ : A 6) NEI A Campephaga flava (P) 5 : ; : { : i ; x x Andropadus milanjensis (M) : é ‘ : X , : x x Chlorocichla flaviventris (P) : : : : x S ; Phyllastrephus cerviniventris (P) X x : Meany ©,5) hare j X x P. terrestris (P) : : : 3 ; ; x K (0) P. placidus (M) : x x ‘ x x x x X x Pogonocichla stellata (M) x x x x x Xx x x x ew Cossypha heuglini (P) X X ‘ : . X : : C. natalensis (P) : ; s : H x x Turdus gurneyi (M) ; i x x Kiet SVR exe T. olivaceus (M) q : ‘ 0) ‘ , : : ; Bradypterus lopezi (M) X i X X x X x x Xx Apalis chapini (M) X O ‘ : X Y i : ala A. flavida (P) i S ; 4 : : X ‘ X X A. thoracica (M) X xX x x X x X x xX x
Camaroptera brachyura (P) i 4 : : : , : : X X
Ecology and biogeography of forest bird communities in Malawi 21
Table 3 contd Kirk Range
E
Se MS = ‘hy o neh aera
= Boy Gs) a ese N CS = 2
obs SO a ae Se eR
No ae Ou 2 N aS co wes Muscicapa adusta (P) x x Xx : x Xx x X x Xx M. caerulescens (P) 4 % - : p ; : ; ‘ Xx Batis capensis (M) : x x a X x x x x Platysteira peltata (P) x : x x Elminia albonotata (M) : x x x x x x x x i Trochocercus cyanomelas (P) 2 : : 5 ; : : : oO Terpsiphone viridis (P) X x ; x xX x X Dryoscopus cubla (P) x x x x x x x x x x Laniarius aethiopicus (P) x x X Xx x x x X Malaconotus olivaceus (M) x x x X x x Cinnyricinclus leucogaster (P) : : F : x : Anthreptes collaris (P) x x x x : ~ x Nectarinia mediocris (M) : 4 x x x x x x x : N. olivacea (P) x x : x x x j x x Zosterops senegalensis (P) x x x Xx x % x x 4 Ploceus bicolor (P) , Z é ; : x Xx x Cryptospiza reichenovii (M) x x : x x : Hypargos niveoguttatus (P) : : : § : : x Total number of species DAS 30)" 14 21°. 28. 2S) 2a Sa Gr 38
* Likely to be under-recorded. > Four more species are recorded from the lower slopes (riverine forest, 1500—1600 m): Sarothrura elegans, Muscicapa adusta, Terpsiphone viridis and Anthreptes collaris.
forest-grassland mosaic rather than in large forest blocks—as on S Viphya. Forest- grassland territory of c. 3 km? per pair on SW Nyika at 2150—2200 m. Also in deciduous forest, miombo and other woodland types. 50-2400 m.
Forest Buzzard Buteo oreophilus. Montane endemic. Table 2: only in extensive submontane forest and never seen hunting outside. Probably no more than 6—7 pairs in 34 km? on E Nyika, and fewer Misuku Hills. 1600-2350 m.
Ayres’ Hawk Eagle Hieraaetus ayresii. Pluriregional (GC). Tables 2, 4. Sparse. Also in various woodland types and deciduous forest. 50-2300 m.
Crowned Eagle Stephanoaetus coronatus. Pluriregional (GC). Hunts in forest as well as outside. Prey remains below a nest (Nyika) of Heterohyrax brucei, Cephalophus antelopes (two species possible: C. natalensis and C. monticola); small rodent carried to nest, and seen chasing monkeys Cercopithecus (mitis) albogularis; a specimen collected by A. Whyte had eaten a young klipspringer Oreotragus oreotragus. Four pairs in 45 km? of forest-grassland on SW Nyika (2000-2200 m) but forage also in woodland below the
Continued on p. 24
22 Francoise Dowsett-Lemaire
Table 4. Bird species proven or likely to breed in the following rain forests of southeast Malawi. submontane and montane (Namizimu, Mangochi, Zomba, upper Mulanje, 1500—2300 m), mid- altitude (Chikala, Lisau to Thyolo, 1170-1600 m, and middle Mulanje 900—2300 m), and lowland (tea estates near Thyolo, lower Mulanje, Malawi Hills, 600-1100 m). Symbols as in Table 2.
Shire Highlands? Mulanje Sete ae g oS 3 as oO Ss S 4 Peg agte G2 3eag ag SSB 8 2885 8 Bae Bird species Z. = ON Ga Ay ay a = Sli SS | = Accipiter tachiro (P) pete, aia, ith), Guth 4 Xe RE RG ee Hieraaetus ayresii (P) x " x Stephanoaetus coronatus (P) MRD OX x x x Guttera edouardi (P) : ue es 5 mayer. Sarothrura elegans (P)° a paella lr ete sre 6.2) x Xx Qua Columba arquatrix (M) Ly eal haces A eco ND) GOAN, o/v ov v x (v) C. delegorguei (P) eee tHe BN Vi tay Sd kate en ; Turtur tympanistria (P) > Se. Si, He), Ga Ge ED GD. Os Aplopelia larvata (M) X XK K KM KR Xe ee eee Tauraco livingstonii (E) ) > Ta a> Ch Ca a im Ge Sipe pc ok T. porphyreolophus (E) Boe Ba I Chrysococcyx cupreus (P) Eh eens, Cement 6,5 Ail 0.5) hap, ae, » Gar, she Dee ‘ Ceuthmochares aereus (P) sh AU sa at mec Xe) Kye ee Strix woodfordii (P)° Neel tio ce Say me XX ke oe eer Schoutedenapus.myoptilus(M) «0. 6 Nee a Apaloderma narina (P) oD, i amr Ar I OAL) So 52 x A. vittatum (M) MD ONE Of ein) No XW) aie eonnee Tockus alboterminatus (P) pat, Caiman, oni KKK KA OR Wen go x Bycanistes brevis (E) inlets Sraheco hgh hhh Vo UW) x B. bucinator (P) 9 are, Gah, aeaaian Be oot Sate KES Ge Ee a a x Stactolaema leucotis (E) bd) yievalgse Oi Digav gat Koy, Ab Marl Ric Nr Xe a NaS x Stactolaema olivacea (E) Sone aN Runa TEI at Ales 6 : Pogoniulus bilineatus (P) rs > Cy Gen abn aula a UNO Cm ENT KS GR ae P.. leucomystax (M) ar ern tee eect nalal (') MRM 5 SE P. simplex (E) RAN Co i Pa iene watt ae 5 OG ee : Indicator minor (P) SARE a Kone ea GO Kops aa axe ec x I. variegatus (P) PRU), C18, Gate Pia). eas Penni KE VN ae x Campethera abingoni (P) Apne, icp, Seem Canter), Gisied, Guana, 4 KX OX Pee x Denropicos fuscescens (P) Air b aD and Sune, lire acyl 05.35 : Smithornis capensis (P)° He idiy Stadia (6") ass 2 Ker x Dicrurus ludwigii (P) > Say, Set, Ge, Mme SM GED. Gi dro G rg SS X Oriolus chlorocephalus (E) EE Greve G4 Mma oat mt OnE PoIN5 Ginn g O. larvatus (P) sili MER OVER NES EKS IN PX Alcippe abyssinica (M) barns CRRA Irae RPT ie MHI HS 2 fy Coracina caesia (M) An Ps PMURO NT jas cnialae a aR Mil. 5g : q Campephaga flava (P) » Pena Mena >, Sih. chino Munk OG iwi (O QOS MoS 2S (v) A. milanjensis (M) Ny > Gi Ue Gliby day Gil Ged a> egies
A. nigriceps (M) Pere Cerne nME EINE HCN ee ND WPS
Ecology and biogeography of forest bird communities in Malawi
Table 4 contd.
Bird species
A. virens (P) Chlorocichla flaviventris (P)
Phyllastrephus cerviniventris (P) x x x
P. flavostriatus vincenti (E) P. placidus (M)
P. terrestris (P)
Nicator gularis (P) Erythropygia quadrivirgata ¢P) Alethe choloensis (M) Pogonocichla stellata (M) Cossypha anomala (M)
C. heuglini (P)
C. natalensis (P)
Turdus fischeri (M)°
T. gurneyi (M)
T. olivaceus (M) Bradypterus lopezi (M) Phylloscopus ruficapilla (M) Apalis chariessa (E)
A. flavida (P)
A. melanocephala (E)
A. thoracica (M) Camaroptera brachyura (P) Muscicapa adusta (P)
M. caerulescens (P)
Batis capensis (M)
B. fratrum (E)
Platysteira peltata (P) Elminia albonotata (M) Trochocercus cyanomelas (P) Terpsiphone viridis (P) Dryoscopus cubla (P) Malaconotus multicolor (P) M. olivaceus (M) Cinnyricinclus leucogaster (P) Anthreptes collaris (P) Nectarinia mediocris (M)
N. olivacea (P)
Zosterops senegalensis (P) Ploceus bicolor (P) Cryptospiza reichenovii (M) Hypargos niveoguttatus (P) Total number of species
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Shire Highlands?
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am mR OK
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23
Malawi Hills
24 Francoise Dowsett-Lemaire
escarpment. Also in mature miombo and riparian woodland, deciduous forest, 50-2350 m.
Marginal species. Six other raptors are known to nest in rain forest, but they hunt in open country: Hooded Vulture Neophron monachus, White-headed Vulture Trigonoceps occipitalis, Red-breasted Sparrowhawk Accipiter rufiventris (from montane grassland, 1700-2400 m, Appendix. 3), Long-crested Eagle Lophaetus occipitalis, Martial Eagle Polemaetus bellicosus, Bateleur Terathopius ecaudatus.
PHASIANIDAE
Scaly Francolin Francolinus squamatus. Pluriregional (GC). Table 2: confined to S Viphya. Ground stratum of forest, also in secondary growth, thick Pteridium bracken, and occasionally penetrates pine plantations. Quite common between Chamambo and Kawandama, and on eastern scarp. 1000—1800 m.
Crested Guineafowl Guttera edouardi. Pluriregional. Tables 2, 4. Ground stratum, in small groups. Also in riverine forest (Luweya and tributaries near Mzuma) and semi- evergreen thicket (Lower Shire). In small numbers, probably threatened. 50-700 m.
Marginal species. Hildebrandt’s Francolin Francolinus hildebrandti, of scrub and thicket (to 2200 m) is occasional in dry or secondary forest near edges, 600—1600 m.
RALLIDAE
Buff-spotted Flufftail Sarothrura elegans. Pluriregional (GC). Tables 2, 3, 4. Certainly under-recorded: forest distribution entirely based on sound data. Calls more often at night, only in the rains, November—March. Also in (semi-) evergreen and deciduous thickets. 500-1900 m. Subject to some movements—e.g. a bird heard once in a Lilongwe garden in December (MGD) must have been passing.
Marginal species. The Red-tailed Flufftail Sarothrura affinis of montane grassland (Appendix. 3) has been heard a few times inside forest, not far from edge (Nyika, 2150 m).
COLUMBIDAE
Two Columba pigeons (one highly local) eat whole fruits in the upper strata, and three doves (one rather marginal) take a mixture of seeds and small invertebrates on the — (see Dowsett-Lemaire 1988b).
Rameron Pigeon Columba arquatrix. Montane endemic. Tables 2, 3, 4. Densities vary according to distribution of favourite fruit trees (especially Afrocrania volkensii, Olea capensis, Polyscias fulva, also Schefflera umbellifera on Mulanje). Important breeding sites (with a few hundred pairs) are the Nyika Plateau, Malosa—Zomba (at least in ‘olive years’ as in 1983) and Mulanje Mts, with highest densities on SW Nyika (2100-2200 m)
Notes to Table 4, pp. 22—23
* Zomba Mt includes adjacent Malosa Mt with identical avifauna; secondary submontane forest
on Chiradzulu Mt has only two species not found lower down at Lisau (Elminia albonotata, Nectarinia mediocris); forest at Mpingwe and Namzadi (Nansadi) mentioned by Benson (1948) no longer exists. > Likely to be under-recorded. Riverine forest at foothills (1050-1400 m) has several species not found on plateau, e.g. Stactolaema leucotis, Dicrurus ludwigii, Andropadus virens, Apalis chariessa, Platysteira peltata, Ploceus bicolor
Ecology and biogeography of forest bird communities in Malawi 25
of 1-3 pairs/3 ha. Breeding pairs there and elsewhere are outnumbered by non-breeders. Unlike breeding birds which roost in their nesting patches, non-breeders on the Nyika roost communally, at two traditional sites 16 km apart (Chowo Forest in Zambia, Pinus plantation on central plateau): they undertake daily feeding movements of up to 20 km.
Numbers in the breeding season (September—November) lowest in Mugesse Forest, Misuku (two song-posts in 200 ha in 1982) and central Malawi. On the Nyika, small patches where Olea capensis provides the main fruit source are occupied by territorial pigeons only in olive years (i.e. every other year), although these birds feed also in other forest patches. The species is of irregular occurrence at Ntchisi and Dzalanyama where there is little suitable food other than olives and it is not (yet) recorded from Mangochi Mt (no fruiting Olea in our 1983 visit).
1500-2300 m. Largely a breeding migrant; some stay and wander locally after the nesting season. A few birds roosting in Uzumara (N Viphya) in June were seen to fly in from Chimaliro, 20 km distant. On the Nyika and elsewhere numbers drop sharply during December, with only a few birds or small flocks left in January—May. Wanderers noted in some mid-altitude forests of the Shire Highlands, and in lowland forest only in Malawi Hills in December to May (Long 1961) and foot of Mulanje Mt at c. 800 m with one bird collected from a flock in early August (Benson 1940), but altitudinal movements down Mulanje not recorded in recent decades. On the Nyika, some dozen birds return in June in Chionanthus fruiting years (and the presence of 40 birds on Ndirande in May (NJS) may be similarly explained), otherwise in August when territorial settlements take place (with Afrocrania fruits starting to ripen). In the north at least, I believe over 90 per cent of birds leave the country in December, presumably moving north.
Bronze-naped Pigeon Columba delegorguei. Pluriregional (GC, as considered conspecific with C. iriditorques: Dowsett & Dowsett-Lemaire 1980). Table 4: confined to Thyolo Mt. Unaccountably rare: no more than one bird seen and another singing in c. 500 ha (November 1983); maximum of two birds heard by Johnston-Stewart (1982) in January—February. 1200-1450 m.
Blue-spotted Wood Dove Turtur afer. Pluriregional. Table 2. Not normally in rain forest, except on the Lake-shore, 500—700 m. Usually in riverine vegetation and moist woodland.
Tambourine Dove Turtur tympanistria. Pluriregional (GC). Tables 2, 3, 4. Widespread evergreen thicket (Lower Shire). In small numbers, probably threatened. 50-700 m.
Cinnamon Dove Aplopelia larvata. Montane near-endemic. Tables 2, 3, 4. Widespread, but not known to nest in forest patches without a stream. Territories of 24 ha/pair on SW Nyika (2000-2200 m) and 2-6 ha/pair on Viphya Plateaux (1600-2000 m). 1050—2300 m, but below 2100 m south of 14°S. Largely resident, with some altitudinal movements to 600—900 m: individuals noted or collected in lowland forest or evergreen thicket at six localities from N Lake-shore (Benson 1940) to Malawi Hills (Long 1967, NJS), including the foot of Mulanje Mt (NJS, pers. obs.), mostly April to August, with one record February and October. Presence in Malawi Hills in December (Long 1967, on sound only) requires confirmation. These movements cover distances of up to 80 km from the nearest breeding sites.
Marginal species. The Pink-breasted Turtle Dove Streptopelia lugens, of montane grassland and scrub (1700—2400 m, Appendix. 3), occasionally flies into edge of forest. The Red-eyed Dove S. semitorquata is rare on forest edges at low and medium altitudes. Green Pigeons Treron australis are regular post-breeding visitors to submontane forest
26 Francoise Dowsett-Lemaire
(1600-2200 m in the north), small flocks feeding on Syzygium and other fruits (Dowsett- Lemaire 1988b) from November or December to March.
PSITTACIDAE
No true forest species, but the Brown-necked Parrot Poicephalus robustus from savanna is a regular post-breeding visitor to submontane forest (S Viphya, Nyika to 2150 m, perhaps Ntchisi) to feed on ripe seeds of Parinari etc. (Dowsett-Lemaire 1988b), from November to February.
MUSOPHAGIDAE
Three Tauraco species take a great variety of fruits, mostly in canopy and mid-stratum (Dowsett-Lemaire 1988b), and occasionally other vegetable matter. The two green Tauraco (livingstonii, schalowi) are completely allopatric, and T. porphyreolophus is largely segregated from either by altitude and habitat, or keeps separate territories.
Purple-crested Turaco Tauraco porphyreolophus. Eastern endemic. Tables 2, 3, 4. Common in lowland forest. Also in semi-evergreen thicket, deciduous forest, riparian and miombo woodland. 50—1600 m, but absent from mid-altitude rain forest occupied by the other species.
Schalow’s Turaco Tauraco schalowi. Pluriregional. Tables 2, 3. Common, with for example 40 pairs in 160 ha on SW Nyika (2100-2200 m). Also in riparian forest and miombo woodland. 1000—2300 m, locally down to 600 m. In rain forest, this and previous species largely replace each other, T. schalowi at higher altitudes. Where they come into contact, in riverine forest and woodland, they maintain separate territories and react to each other’s song.
Livingstone’s Turaco Tauraco livingstonii. Eastern endemic. Table 4. Common, replacing T. schalowi east of Rift. The fruit diet identified so far greatly overlaps with that of T. schalowi (80 per cent species in common). Also in riparian forest and pees woodland. 1000-2300 m, down to 600 m at Mulanje.
CUCULIDAE Four species from different genera, all of localized distribution.
Barred Long-tailed Cuckoo Cercococcyx montanus. Eastern endemic. Table 2: confined to Lake-shore forests. Niche uncertain, and calling season of Lake-shore birds apparently very restricted (December). Also in deciduous forest and thicket in southern Malawi where status uncertain following habitat clearance. 50-700 m. Perhaps mainly a rainy season visitor, but one bird mist-netted in June in the Lower Shire (Benson & Benson IQA 23)
Emerald Cuckoo Chrysococcyx cupreus. Pluriregional (GC). Tables 3, 4. Local in forest canopy, mostly at medium altitudes. Also in deciduous forest, semi-evergreen thicket and miombo woodland. 50-1700 m.
Green Coucal Ceuthmochares aereus. Pluriregional (GC). Tables 2, 4. In dense understorey, edges and mid-stratum where leafy tangles of lianes. Local, common only in Lake-shore forests. Also in (semi-) evergreen thicket. 50-1300 m.
White-browed Coucal Centropus superciliosus. Pluriregional. Table 2. Not normally in rain forest except in thick understorey of Lake-shore forests, 500-700 m. In any thicket, secondary growth (to 2200 m), reedbeds, gardens.
Ecology and biogeography of forest bird communities in Malawi 27
Marginal species. Red-chested Cuckoos Cuculus solitarius from woodland and thicket often call from edges of forest and montane scrub (to 2250 m) and are known to parasitize robins of forest margins Cossypha caffra and C. heuglini (pers. obs., Benson & Benson 1977). The Klaas’s Cuckoo Chrysococcyx klaas is of more local occurrence at edges, to 2200 m.
STRIGIDAE
Wood Owl Strix woodfordii. Pluriregional (GC). Tables 2, 3, 4. Widespread in all forest types. Defended territory of a pair on Nyika at least 10 ha, but home range nearer 50 ha. Also in thicket, miombo and other woodland. 50-2400 m.
APODIDAE Scarce Swift Schoutedenapus myoptilus. Montane endemic. Tables 2, 4. Feeds essen- tially over forest canopy; all forest areas where located other than on passage are at least 150 ha in size in the north, over 300 ha in the south, and have a tall canopy (25—40 m). Common and very vocal, with several dozen pairs in Misukus, on Nyika, Mulanje and Thyolo Mts; aerial matings frequently seen from late October to December. The nest of this widespread swift is still undescribed; although it may breed on cliffs locally (suspected for Kenya: Brown & Britton 1980; eastern Zimbabwe: C.J. Vernon and M.P.S. Irwin, in litt.), itis likely to breed in forest trees in Malawi, at least in the north. A swift found on the forest floor in Chowo, Zambian Nyika, in January (Scott 1979) was a newly- fledged young, judging from photographs. Cliffs are virtually absent from its breeding range in northern Malawi, and it was never seen near rocky banks of streams. 1600-2350 m north of 14°S, c. 1200-2000 m in the south. A breeding migrant. First arrivals 1 September (Nyika) and 3 September (Zomba, on passage); all September records are of birds passing over. Settle from late October or early November and common until March, then suddenly disappear. Latest date 12 April (Nyika). Also wandering over the town of Mzuzu (1300 m) in November and January.
COLIIDAE
Only one marginal species, the Speckled Mousebird Colius striatus, from thicket and montane scrub (to 2200 m), which takes fruit from small trees on the edge (Dowsett- Lemaire 1988b).
TROGONIDAE Two species largely separated by altitude. Both snatch prey (large insects) in short flights off foliage and bark in the understorey.
Narina’s Trogon Apaloderma narina. Pluriregional (GC). Tables 2, 3, 4. In dense understorey (2-18 m), less easily seen than next species. Often in very small numbers, local, or patchily distributed, but throughout Chikala Forest (1300-1550 m). Only a rare visitor to Thyolo Mt (one recent February record, JDA); overlaps with A. vittatum at Ntchisi (1400-1600 m). Also in (semi-) evergreen and deciduous thicket, and transition woodland (i.e. moist miombo with some evergreen understorey). 50-1600 m, below 1000 mon S Mulanje. Subject to local movements, wandering to gardens, plantations and irregular in some forest localities (Kalwe, Thyolo).
Bar-tailed Trogon Apaloderma vittatum. Montane endemic. Tables 2, 3, 4. Hunts in mid- stratum (mostly 4-20 m) under fairly closed canopy. Prey (especially caterpillars, moths) is located from horizontal perches, snatched off bark and twigs whatever the angle (even vertical trunks) and taken to another perch to eat. Reaches its highest density (12 pairs in 25 ha) under closed canopy in Chowo Forest, Zambian Nyika (2100-2200 m); often 2-3
28 Francoise Dowsett-Lemaire
pairs/10 ha in other northern forests (Misuku, N Viphya) where canopy is less contiguous. Small numbers in south-central Malawi: only a few pairs on Chirobwe Mt (eastern scarp where there is tall forest), 3 pairs and 1 male in c. 250 ha on Thyolo Mt (in 1983, probably no more than a dozen pairs in the whole forest), 1 pair on Soche (150 ha, but forest now degraded), more evenly distributed on Mulanje Mt 1600-2000 m.
1300-2200 m, below 2000 m in the south. Largely resident; some altitudinal and especially inter-montane movements up to 100 km from the nearest established popula- tion. Altitudinal, off-season movements are of single birds noted in lowland forest at c. 1050 m near Thyolo (NJS), down Mulanje and on the slopes of Zomba Mt at c. 1200 m in July-August (Benson & Benson 1975); there is an old specimen from Chiradzulu/Lisau (July). But more wanderers (at least seven) have been found at mid or high elevations (1300—2200 m) in the period late August to December—when territorial activity is most intense among breeding pairs: S Viphya (Chamambo: Benson 1940, JDA in 1981), Mangochi Mt (Dowsett & Hunter 1980), Zoinba Mt (pers. obs.), Bangwe (NJS), Malabvi (pers. obs.). On the Nyika individuals often wander to small isolated patches of forest, up to 12 km from the nearest regular site. Mangochi Mtis 100 km from the nearest population (Chirobwe across the Rift) and 150 km from the second nearest (Mulanje). These movements show remarkable exploratory behaviour; all forests visited appear too secondary, with a low canopy, or too small, to encourage settlement.
PHOENICULIDAE Only marginal: one woodland species, the Scimitarbill Phoeniculus cyanomelas, rarely wanders to forest (up to 2200 m, Nyika), feeding in canopy.
BUCEROTIDAE
One small Tockus, with a diet of large insects and small vertebrates (e.g. chameleons) and few fruits; two large Bycanistes essentially frugivorous, both with a predilection for figs (Dowsett-Lemaire 1988b) and almost allopatric. All three occasionally take flying ants on the wing.
Crowned Hornbill Tockus alboterminatus. Pluriregional. Tables 2, 3, 4. Widespread in canopy of tall forest; absent from secondary, low submontane forest in the central highlands (Dedza and Kirk Range). Densities vary from 1 pair/10 ha to 1 in 50 ha in the submontane forests of the north. Also in deciduous forest, miombo and other woodland. 50-2000 m, locally to 2200 m (SW Nyika).
Silvery-cheeked Hornbill Bycanistes brevis. Eastern endemic. Tables 2, 3, 4. Incanopy and subcanopy, sometimes lower on forest edges and clearings, even coming to the ground there. In large numbers only where figs are plentiful (Misuku, locally foot of Mulanje), with moderate numbers Malawi Hills, very few elsewhere (central highlands). 600-2000 m. The Misuku population (140-200 birds) is migratory, the majority of birds leaving after breeding, for several months from December or January (I. Bampton and Fr. Tréguier have observations over several years). Many records of wanderers in the country (e.g. Benson & Benson 1975), in the north as far as the high Nyika (2200-2300 m) 100 km from Misuku.
Trumpeter Hornbill Bycanistes bucinator. Tables 2, 4. In canopy, shyer than previous species. Numerous only where figs abound (Ntchisi, Thyolo Mt); at higher altitudes, pairs are widely scattered (e.g. 3 pairs/110 ha on SW Nyika, 2000 m). The distribution of the two Bycanistes overlaps only in the Malawi Hills, and marginally at the foot of Mulanje Mt where bucinator is outnumbered by brevis and perhaps merely a visitor. Also in deciduous and riparian forest, thicket and miombo woodland. 50-2150 m. Subject to local
Ecology and biogeography of forest bird communities in Malawi 29
wanderings, and at high altitudes may be mainly a breeding migrant—e.g. absent Nyika from March to August, but seen Musisi (1700 m) in June.
CAPITONIDAE
Two Stactolaema barbets, only marginally sympatric, and three small Pogoniulus tinkerbirds, the two siblings /eucomystax and simplex being allopatric. Both Stactolaema are partial to figs; P. leucomystax is a mistletoe (Loranthaceae) specialist (Dowsett- Lemaire 1988b); all five also take insects.
White-eared Barbet Stactolaema leucotis. Eastern endemic. Table 4. In canopy and mid-stratum of lowland and mid-altitude forests where strangling fig trees (Ficus lutea, F. sansibarica, F. thonningii, etc.) not uncommon. Takes some insects on the wing. Also in riparian forest and woodland with fig trees. 600-1600 m (but not above 800 m on S Mulanje where fig trees become sparse). Some local wandering.
Green Barbet Stactolaema olivacea. Eastern endemic. Tables 2, 4. Confined to two forest sites where figs of several species are plentiful. Some pairs hold territories of 10—15 ha in the Misuku Hills, and the total population there could be of the order of 200 pairs (1600-1900 m, less common 1900-2000 m). Common on Thyolo Mt (1170-1450 m), outnumbering S. /eucotis above 1300 m, but total population below 80 pairs.
Moustached Green Tinkerbird Pogoniulus leucomystax. Montane endemic. Tables 2, 3, 4. Widespread, except in southeast (Mulanje only). In all forest strata and edges (wherever mistletoes); insects are also an important part of the diet and are caught mostly by flycatching in gaps of the mid-stratum. Its breeding distribution in upland forest is correlated to the presence of at least 4-6 mistletoe species, 1.e. providing berries (almost) all year round. Often quite common, especially where forest is fragmented (1-2 pairs/ha on SW Nyika, with the mistletoe Englerina inaequilatera frequent on edges), less so in continuous forest. Very local on the slopes of Mulanje Mt (1400—2000 m), as are its main food plants.
1300—2300 m. Largely resident, with some altitudinal or inter-montane movements of up to 70 km or more. Wanderers noted in May-July: below the Misuku Hills at 1100-1200 m (Benson 1937, 1953a), Rumphi Gorge at 1100 m (Benson 1953a) and the eastern scarp of S Viphya at 1200-1400 m (several, pers. obs.). Individuals also wandering to Chipata Mt (June, Benson 1940), Chimbia in Kirk Range (May, NJS) and as far as Soche Mt (October, JDA).
Yellow-rumped Tinkerbird Pogoniulus bilineatus. Pluriregional (GC). Tables 2, 4. Feeds at all levels and on edges; has a more generalized fruit diet than /eucomystax and is common in the Liwonde (Chikala) Hills and Shire Highlands where the mistletoe flora is poor. Also takes insects by flycatching and foliage gleaning. Overlaps with leucomystax on Viphya Plateaux and foot of E Nyika, 1600—2000 m, but absent in central Malawi (Ntchisi to Kirk Range) and the extreme north where coexistence with /eucomysStax is perhaps not possible. Also in riverine forest, semi-evergreen thicket (Lower Shire) and moist transition miombo woodland (E Viphya, where the woodland Yellow-fronted Tinkerbird P. chrysoconus is absent). 50-2000 m.
Eastern Green Tinkerbird Pogoniulus simplex. Eastern endemic. Table 4. Replaces leucomystax east of the Lake where quite numerous. The Mangochi—Namizimu forests are rich in mistletoes; whether this species is as dependent on them as /eucomystax has not been studied. Also in nearby lowland riparian forest and Lake-shore thicket. 500-1700 m.
30 Francoise Dowsett-Lemaire
INDICATORIDAE Two forest-woodland species whose distribution is influenced by that of their nest hosts (barbets in one, woodpeckers in the other).
Lesser Honeyguide Indicator minor. Tables 3, 4. In canopy and mid-stratum, taking insects (on the wing or from foliage) and beeswax. Known to parasitize Stactolaema leucotis near Thyolo (NJS) and suspected to do so elsewhere (Ndirande, Chikala) as seen visiting nest holes or attempting to do so and persistently chased by these barbets. Its distribution in forest (restricted to low and mid-altitude forest in the south) almost matches that of this particular host. Surprisingly only one song-post was located in forest (Thyolo Mt). Also in all woodland types and deciduous forest. 50-1500 m, wandering to 2200 m (Nyika, outside forest). Has other hosts in woodland (Benson & Benson 1977).
Scaly-throated Honeyguide Indicator variegatus. Pluriregional. Tables 2, 3, 4. Canopy and mid-stratum; takes insects by flycatching or sallying to bark and foliage, and beeswax. Once at an ant swarm, pecking prey on trunk that was fleeing above ants. Widespread, but individuals always seem on the move when feeding, and have probably very large home ranges. A soft whistle fue-fue-fue-... (emitted by both adults and fledglings: Short in Fry et al. 1988) is not infrequent, but only three song-posts of males have been located in rain forest (Lisau, two sites on Mulanje) and one in secondary forest (Dzonze), suggesting very wide ranging movements of visiting females to woodland areas. Parasitizes Dend- ropicos griseocephalus in the north (Dowsett-Lemaire 1983b: of 22 woodpecker pairs in c. 100 ha of forest patches on SW Nyika, three were parasitized in the same season in neighbouring patches of 1.3, 2.3 and 8 ha, probably the work of the same female honeyguide) and D. fuscescens in the south (Johnston-Stewart 1982). Also in miombo woodland, riverine and deciduous forest. 50-2300 m.
Marginal species. The Eastern Least Honeyguide /ndicator meliphilus is of uncertain status: singles seen twice on the Nyika in two-and-a-half years, also recorded from forest on Mulanje and Thyolo Mts (Benson & Benson 1977).
PICIDAE Two Dendropicos species, allopatric, but each coexists with Campethera abingoni which has different feeding techniques and very low densities.
Golden-tailed Woodpecker Campethera abingoni. Pluriregional. Tables 2, 3, 4. Probes and gleans small insects (often ants) on bark of trunks and branches; does not excavate for food, unlike Dendropicos. Its distribution in forest is extremely patchy, although a feeding territory when breeding is c. 10-15 ha. Also in miombo woodland and deciduous forest. 50-2200 m.
Olive Woodpecker Dendropicos (Mesopicos) griseocephalus. Montane near-endemic. Table 2: south to S Viphya. Taps and probes, or excavates large insects (often larvae) from bark, mostly in the upper levels of trunks and on small branches. Prefers soft bark of fast- growing trees (near edges and in gaps) so that its density in an area of very fragmented forest is considerably higher than in large blocks: thus 22 pairs in 100 ha of small patches (0.1-12 ha) on SW Nyika (2150-2200 m, Dowsett-Lemaire 1983a) against 2—3 pairs in forests of 100-150 ha. 1200-2450 m. Basically resident, with wanderers collected in riparian forest on SW slopes of Nyika (c. 1200 m) and Rumphi Gorge (1100 m) in August (Benson 1940), some 20 km from nearest occupied submontane forest.
Cardinal Woodpecker Dendropicos fuscescens. Pluriregional. Tables 3, 4. Feeds on bark like previous species, at all levels from base of trunk to canopy. Apparently excluded
Ecology and biogeography of forest bird communities in Malawi 31
from forest in the north by its congener. Also in all woodland types and deciduous forest. 50-2100 m.
EURYLAIMIDAE
African Broadbill Smithornis capensis. Pluriregional (GC). Tables 2, 3, 4. Likely to be under-recorded. Flycatches and sallies to foliage for insects, in dense lower storey and mid-stratum, sometimes in canopy. In northern forests appears commoner below 1500 m, but densities difficult to assess as it is rather elusive, and aerial displays are performed mostly i in brief twilight hours; several birds heard in c. 20 ha at 1800 m (Misuku). Also in riparian forest, semi-evergreen thicket and moist transition woodland: 50—2050 m, but not above 1500 m south of 14°S. -
HIRUNDINIDAE Only marginal, with the Black Saw-wing Psalidoprocne pristoptera (to 2000 m) and White-headed Saw-wing P. albiceps (montane, 1200—2300 m, Appendix 3) often feeding along forest edges.
MOTACILLIDAE Only marginal. The Mountain Wagtail Motacilla clara penetrates forest along rocky fast- flowing streams, at least up to 2000 m (Nyika) and 1800 m (Mulanyje).
DICRURIDAE
Square-tailed Drongo Dicrurus ludwigii. Pluriregional (GC). Table 4. In canopy and dense mid-stratum, flycatching and snatching insects from foliage. At least 1 pair/ha in some places (Thyolo, Mulanje). Also in deciduous forest, and evergreen, riparian thicket (Lower Shire) where hunts much lower. 50—1600 m. Curiously confined to the southeast: forest at low altitudes perhaps not sufficiently well developed in the north.
ORIOLIDAE ; Have a mixed insect—fruit diet; only one stenotypic forest species, in the southeast.
Green-headed Oriole Oriolus chlorocephalus. Eastern endemic. Table 4. Gleans or snatches from foliage in tall canopy, sometimes flycatches in mid-stratum. In lowland forest near Thyolo (1050 m) territorial pairs occupy from 13 to 25 ha. About 15 pairs were counted on Chikala Hill (mostly 1300-1400 m, none above 1450 m); becomes rare above 1300 m on Thyolo Mt. The total Malawi population was estimated in 1983 at between 55 and 60 pairs. 1000—1450 m. Records on Lisau (40 km from Thyolo, 70 km from Chikala) are of wanderers in the non-breeding season (collected in July 1895, seen in January 1981 by NJS). The status of birds previously noted from Soche Mt (Benson 1948, no months given) was not specified: the altitude at which primary forest remains today (1500 m) appears unsuitable, and it may be too small anyway.
Eastern Black-headed Oriole Oriolus larvatus. Pluriregional. Tables 2, 3, 4. In canopy. Status in rain forest unclear: does not breed on the Nyika, but several present and noisy from mid-April to October, which overlaps with the main breeding season in woodland (September-November: Benson & Benson 1977). Recorded in the Shire Highlands in September—October but not December; however, throughout the rains at Ntchisi and in some of the Lake-shore forests. In any woodland and deciduous forest. 50-2000 m, wandering to 2300 m (Nyika).
Marginal species. The African Golden Oriole Oriolus auratus (from woodland) is an occasional non-breeding visitor to submontane and mid-altitude forest (on the Nyika, from April to October).
32 Francoise Dowsett-Lemaire
TIMALIIDAE
African Hill Babbler Alcippe abyssinica. Montane endemic. Tables 2, 4: Mangochi is at southern limit of range. Mostly in mid-stratum thickets (4-16 m) with walls of lianes. Gleans insects, fruits, sometimes hovers; seen once attending an ant swarm, pecking small prey in foliage above ants. Its optimum habitat is best developed under tall but discontinu- ous canopy, and locally it reaches densities of 4—5 pairs/10 ha (Nyika at 2000 m, Uzumara at 1800 m). Only one bird calling at Namizimu in a patch of 32 ha (Mapalamba Hill), and a few located on Mangochi Mt in October 1983—the suitable habitat seems rather local— where Dowsett & Hunter (1980) found it ‘numerous’ in October 1972; but the number of birds collected then (11) must have affected this isolated population. 1550—2400 m.
Mountain Illadopsis Trichastoma pyrrhopterum. Montane endemic. Table 2. In im- penetrable shrubby thickets 2-4 m high often lining streams (Acanthaceae Anisotes, Mimulopsis) or on slopes (Alchornea, Dracaena fragrans); probes and turns over dead leaves and other vegetation debris for small arthropods, mostly 0.2—2 m above ground, but also on floor and occasionally hopping up to 4 m. Rarely seen, but common at Uzumara where heard in every streambed on the northeast slopes, more scattered on E Nyika, local in the less luxuriant forest of Chimaliro. 1600—2300 m.
CAMPEPHAGIDAE
Black Cuckoo-shrike Campephaga flava. Pluriregional. Tables 2, 3, 4. Gleans insects in foliage of canopy and edges, or snatches them in short hops or flights from under leaves or against branches. Has a very patchy distribution in rain forest, especially above 1500 m. Does not breed every year on SW Nyika (above 2000 m). Also in miombo and other woodland, and thicket. 50-2150 m, but probably not breeding below 700-900 m; most birds move out of the plateau areas in April-May to September.
Grey Cuckoo-shrike Coracina caesia. Montane near-endemic. Table 4: unaccountably confined to Thyolo Mt (1170-1450 m) though not uncommon there, especially on edges. Feeds like previous species, also hops and picks insects on branches. Records of isolated birds at two other localities are almost certainly of wanderers: one was collected in April 1944 at Chiradzulu/Lisau by C.W. Benson (specimen in BM), and another in riverine forest on the N scarp of the Malawi Hills in June (at c. 650 m, Long 1976, with a possible sight-record again in December) some 80 km from Thyolo and Chiperone Mt in adjacent Mozambique (where reported by Benson 1950).
Marginal species. The White-breasted Cuckoo-shrike Coracina pectoralis (from wood- land) was seen several times in forest in the Malawi Hills in mixed bird parties in August, but not December.
PYCNONOTIDAE
Eleven taxa, belonging mostly to the genera Andropadus (4) and Phyllastrephus (5), with a maximum of five locally in submontane forest (Table 2) and six in mid-altitude forest (Table 4), i.e. up to 2-3 Andropadus and 34 Phyllastrephus. Fruit is only incidental in the diet of Phyllastrephus (taking mainly small arthropods on bark or forest floor) but much more important in the mixed diet of Andropadus spp. (feeding more in foliage, including the canopy). The fruit diet of the best-known species, A. nigriceps, is extremely wide (Dowsett-Lemaire 1988b, see under A. tephrolaemus); the latter is the only bulbul regularly attending Dorylus ant swarms (and see Willis 1983). Andropadus nigriceps and A. masukuensis are allopatric, so are the two incipient species Phyllastrephus flavostria- tus alfredi and P. f. vincenti.
Ecology and biogeography of forest bird communities in Malawi 33
Eastern Mountain Greenbul Andropadus nigriceps. Montane endemic. Tables 2, 4. One of the most numerous birds at high altitudes. Feeds at all levels of understorey to canopy, and on edges; gleans from bark and foliage, flycatches, and when attending ant swarms (for prey flushed by the ants) snatches in short flights or hops from low perches, or pounces on the ground. An ant swarm is often followed by 6—7 birds, some trespassing territorial boundaries. Also in montane scrub 2-4 m high. Reaches its highest densities in forest—grassland mosaic with 2-3 pairs/ha (SW Nyika, 2100-2200 m); nearer 1 pair/ha in more continuous forest, or less (1 pair/2 ha on N Viphya where A. milanjensis is as common or more so).
1500-2450 m. Largely resident (ringed birds on the Nyika wander up to 2.5 km: Dowsett 1985), with some altitudinal movements. A few come down Mulanje Mt to 700-1000 m in May—August (pers. obs., NJS), also noted at Zomba (1050 m, June: Belcher 1930), and below E Nyika (c. 1350 m, July: Benson 1940); a specimen collected by A. Whyte on the N Lake-shore at 500 m (10°04S, June) must have travelled at least 30 km from the nearest mountain (Nyika).
Stripe-cheeked Greenbul Andropadus milanjensis. Montane endemic. Tables 2, 3, 4. Feeds much like previous species (with considerable overlap in fruit diet: Dowsett- Lemaire 1988b) but less often in lower storey, and is much more skulking. Occasionally attends ant swarms; seen picking insects on ground just outside forest. Overlaps with A. nigriceps at submontane levels (mostly 1500—2000 m), but is the only Andropadus in the upper strata of mid-altitude forest. Densities vary greatly in different areas, and are often inversely related to numbers of A. nigriceps: this may reflect competition, as well as a preference by A. milanjensis for wetter and more luxuriant forests. In the north reaches highest densities in the Misuku Hills (where congener absent) and N Viphya, i.e. at least 5 pairs/10 ha. Elsewhere, in smaller numbers than nigriceps: rare at Jembya (a few scattered pairs at 1850-1920 m), and spaced out on S Viphya. The only Andropadus bulbul in the secondary submontane forests of central Malawi where rather local. Common east of the Rift at medium altitudes (especially 1200-1800 m). Also in riverine forest at Zomba (c. 1100 m).
Mostly 1100-2000 m in the north (uncommon to 2250 m on E Nyika) and 1000-2000 m south of 14°S, but below 1850 m on Mulanje. Largely resident, but regular movements down Mulanje to 600-900 m in February—August (pers. obs., NJS). Also recorded in riparian growth at Misuku at c. 1400 m in August by Benson (1937), but could reside at that altitude.
Shelley’s Greenbul Andropadus masukuensis. Montane endemic. Table 2: Misuku Hills only. At all levels to canopy, gleaning insects swiftly from bark of trunk and smaller branches, also in leafy tangles of lianes and shrubby ground thickets (Dracaena, Acanthopale). Fairly common, but densities difficult to assess as song is rather spasmodic and not far-carrying. 1600—2000 m; also recorded in riparian forest at c. 1300 m in August (Benson 1937).
Little Greenbul Andropadus virens. Pluriregional (GC). Tables 2, 4. In dense under- storey and ground thickets, where a skulker, but takes fruit occasionally up to the canopy. Densities vary greatly, depending partly on luxuriance of understorey. Quite common in several submontane forests of the north below 1900 m (2-6 pairs/10 ha locally in Misukus and N Viphya), though absent at similar altitudes on E Nyika and parts of S Viphya where forests may be too cold and exposed. Almost absent from submontane forest in the south (Mangochi Mt excepted), local in the drier mid-altitude forests (e.g. Lisau) to very
34 Francoise Dowsett-Lemaire
common in the wetter types (e.g. Thyolo). Very common in Lake-shore lowland forest (with dense and moist understorey), but absent from the Malawi Hills (drier, more open). Also in riparian forest with dense lower storey (mostly in the north). 500-2050 m, but 600-1600 m south of 14°S.
Yellow-bellied Bulbul Chlorocichla flaviventris. Pluriregional. Tables 2, 3, 4. Local, in rather secondary forest (scrubby, or with thickets as on the Lake-shore). Mostly in deciduous or evergreen thickets, riparian and transition woodland. 50-1700 m.
Grey-olive Bulbul Phyllastrephus cerviniventris. Pluriregional. Tables 2, 3, 4. Pecks small invertebrates on ground, bark and foliage at low levels (OQ—4 m) in liane and shrubby tangles, usually near streams (with local exceptions, e.g Chipata Mt where it occupies Metarungia ground thickets throughout the forest) and thus very patchily distributed. Moves in big hops, often flicking tail. Also in riparian forest and (semi-) evergreen thickets. 500-1900 m. Possibly competes with P. placidus at medium and high altitudes, and niche expansion noted on Chipata Mt may be related to absence of congener.
Yellow-streaked Bulbul Phyllastrephus flavostriatus alfredi. This well-marked race (Dowsett & Dowsett-Lemaire 1980) is a Montane endemic; the species as a whole is an Eastern endemic. Table 2. Gleans from trunks of trees and lianes, and along branches, mostly in middle and upper strata (above 4 m), occasionally down to 1—2 m high in low thickets. Attracted to bark covered with mossy epiphytes and various vegetation debris, progressing upwards in short hops, with frequent flicks of one or other wing—perhaps to flush prey. Often quite common, with 3-4 pairs/10 ha (Jembya, Musisi, N and S Viphya, larger forests of SW Nyika, 1600-2150 m), more scattered in cool forests of E Nyika.
1400-2300 m. Resident, with some wandering. On Nyika, birds occasionally visit isolated patches up to 10 km from nearest regular site; one bird seen by NDH on Chipata Mt in June must have travelled at least 32 km (from Ntchisi) across woodland. Altitudinal movements suspected at Kawandama (1750-1850 m) as this noisy bird, common in November—December, could not be found in May—but remains fairly numerous at this altitude and higher elsewhere in winter.
Yellow-streaked Bulbul Phyllastrephus flavostriatus vincenti. Eastern endemic. Table 4. Much the same niche as previous race, although tree trunks in lowland forest (Malawi Hills) and drier types of mid-altitude forest (e.g. Lisau) are often devoid of epiphytic growth. Whether this affects densities should be verified. 600-1600 m. Absent from submontane forest, except for some off-season movements on Mulanje to 1800 m (March—August, NJS).
Placid Bulbul Phyllastrephus placidus. Montane endemic. Tables 2, 3, 4. Feeds on ground, pecking or turning over leaves, and in low shrubs and thickets, usually below 1—2 m; hops about flicking tail up and down when at rest, and occasionally one wing. Attends ant swarms. In the Misuku Hills (where P. flavostriatus is absent) its niche has expanded and birds frequently forage up to 6-7 m, sometimes clambering up trunks and lianes to a height of 16 m. In the north is largely allopatric with P. flavostriatus: only really common in the Misuku Hills (especially 1600-1900 m), much the scarcer of the two where they coexist (S Viphya, and only one sighting at Uzumara): South of 14°S appears more strictly terrestrial (rarely seen above 1 m, except on Zomba Mt exploring trunks up to 6-7 m in the absence of flavostriatus) and common next to the local form of flavoStriatus in several mid-altitude forests of the southeast.
1050-2000 m, down to 900 or even 700 m on Mulanje. Resident (e.g. same territory occupied 1980-86 in a small patch on S Viphya) with some local wandering; at
Ecology and biogeography of forest bird communities in Malawi 35
Kawandama (c. 1800 m) much more conspicuous in May than in November—December. A specimen collected by A. Whyte at ‘Songwe’ (Misuku) in July, presumably on the river of that name, may indicate downward movement.
Terrestrial Bulbul Phyllastrephus terrestris. Pluriregional. Tables 2, 3, 4. On ground, occasionally hopping up into dense understorey (below 1 m). Not uncommon in some lowland forests (Lake-shore, Malawi Hills), but at higher elevations only in the drier (e.g. Lisau) or more secondary forests (e.g. Dzonze). Also in (semi-) evergreen and deciduous thickets. 50-1750 m (below 800 m on S. Mulanje), exceptionally to 2050 m in June on S Nyika (Nkhonjera, forest edge) perhaps as wanderers.
White-throated Nicator Nicator gularis. Pluriregional (GC if conspecific with Western Nicator N. chloris, Appendix 1). Tables 2, 4. Ground and dense understorey where very skulking. Highest densities in the Lake-shore forests (SO0O—-700 m) and Kaningina Hills (1100-1200 m) with 3-5 pairs/10 ha. Also in thickets (deciduous and evergreen). 50—1400 m, but only below 1200 m in the south (and below 800 m on S Mulanje).
Marginal species. The Common Bulbul Pycnonotus barbatus (from woodland, thicket, riparian forest, gardens, etc.) often visits the canopy near edges, at all altitudes to 2300 m, but is not so far known to breed in rain forest. Could do so on Dedza Mt, where it is quite common in scrubby forest on the top, and no other arboreal bulbul is present.
TURDIDAE
Thirteen species of seven genera, with a main diet of small arthropods taken mostly on or near the ground; fruits are also eaten by some Cossypha, and Turdus spp. (perhaps on a regular basis, Dowsett-Lemaire 1988b). Several follow Dorylus ant swarms persis- tently, especially the two Alethe, Pogonocichla, Cossypha anomala and C. natalensis at medium and high altitudes (ants are not very active by day in the warmer lowland forests). Sheppardia sharpei does so in an opportunistic manner and Turdus spp. show little interest (see also Willis 1985). There is geographical replacement between the two Alethe, and altitudinal replacement between Cossypha anomala and C. natalensis, and between the two Sheppardia; Pogonocichla seems excluded from medium elevations in the north by Sheppardia gunningi. Two Turdus often coexist, but all three do so only locally (Thyolo and Mulanje Mts).
Eastern Bearded Scrub Robin Erythropygia quadrivirgata. Pluriregional (perhaps conspecific with Central Bearded Scrub Robin E. barbata). Tables 2, 4. Ground stratum, under dense understorey. About 1 pair/ha in some Lake-shore forests (Kalwe, part of Nkuwadzi), but much more local elsewhere (e.g. Malawi Hills). Also in deciduous and evergreen thickets. 500-700 m in the north, 50-1300 m south of 14°S (below 800 m on S Mulanje).
Thyolo Alethe Alethe choloensis. Montane endemic. Table 4; almost endemic to southeast Malawi (Chapter 10). Feeds usually at ant swarms, catching small arthropods (including spiders) flushed by ants, from ground, logs, low trunks, etc., by pouncing from low perches or hopping and pecking. One specimen obtained by Vincent (1935) on Thyolo had its stomach distended with driver-ants and a few small beetles. Occasionally hunts away from ants, even in the wet season (when ants are most active). Highest densities in moist mid-altitude forest, e.g. 2 pairs/10 ha on Thyolo Mt. The total Malawi population was estimated in 1983 at c. 1500 pairs (200 on Thyolo Mt, 1000 m on Mulanje—decreasing with forest clearance). 1200-1900 m, down to 900 m on S Mulanje. Limited altitudinal movements to 700-850 m down Mulanje Mt in March—October (pers.
36 Francoise Dowsett-Lemaire
obs., NJS) though some may stay to breed (one caught in November at 750 m by T. Roberts).
White-chested Alethe Alethe fuelleborni. Montane endemic. Table 2. Feeds at ant swarms like previous species, but very rarely seen away from ants (hopping on leaf litter) and then only in the dry season, when ants may remain inactive for some weeks. One seen picking small workers on a trunk in quick succession. All breeding territories (Nyika) contain an active nest of ants and vary from 0.5—4 ha in small patches. Overall densities in continuous forest are often 2 pairs/10 ha (SW Nyika, Misuku, N Viphya, 1600—2200 m), with smaller numbers elsewhere.
1600-2400 m. There is a record of an altitudinal migrant (female) to streamside vegetation in the Misukus at c. 1380 m (August, Benson 1937), and from ringing data some birds (mostly females) are thought to move out of the Nyika forests in April—September. The sex ratio of adults caught on SW Nyika in October—March varied from 0.5 to 1 female per male (n = 8 to 25 per month). Some colour-ringed females had disappeared in April; in June and September only one definite female was retrapped against six and five males respectively and two unsexed (sexing was done during the breeding season, using cloacal characters: Dowsett 1983). Highly elusive in the dry winter months, the species could easily be overlooked at lower altitudes.
For more details on ecology, vocal behaviour of both species and breeding of fuelleborni see Dowsett-Lemaire (1987).
Gunning’s Akalat Sheppardia gunningi. Eastern endemic. Table 2; also in small mid- altitude forests east of Uzumara and near Mzuzu. In dense understorey of shrubs and woody tangles of lianes, usually below 2 m. Picks small prey on ground, logs and low branches by hopping, or dropping from low perches; turns over leaves. Seen once coming to an ant swarm (600 m). Densities of 1—2 pairs/ha in the Lake-shore forests, and 6 pairs in 7.5 ha on Choma Mt (1750 m); somewhat patchily distributed in the more secondary forests of the Viphya scarp. The total Malawi population of the endemic race bensoni must be well over 3000 pairs (of which at least 1800 pairs in the 1500 ha of forest left on the Lake-shore). 500-1400 m, with an isolated population on the small Choma Mt at 1750 m, and even at that altitude is completely exclusive of Pogonocichla stellata in the breeding season.
Sharpe’s Akalat Sheppardia sharpei. Montane endemic. Table 2. In dense understorey of shrubs and tangles of creepers, usually below 2 m; often attends ant swarms, but also frequently away from ants in impenetrable shrubberies. Pecks small prey on ground, logs and low branches like previous species, but is much swifter in its movements, darting about. Commonest in Uzumara on the northeast slopes (400 ha), with densities of at least 10 pairs/10 ha. More spaced out, but throughout the E Nyika forests; very local on SW Nyika, with 25-30 pairs in a single forest (75 ha, Zambian side) apparently wetter than neighbouring patches at a similar altitude (2000 m). 1600-2300 m. Could have been missed at Musisi if very local, but the understorey is not dense and does not appear very suitable. If the altitude at which the specimen collected by J. McClounie in 1902 is correct (i.e. 1500 m), this record could refer to a wanderer, as there is only riverine forest at that level.
Starred Robin Pogonocichla stellata. Montane endemic. Tables 2, 3, 4. The most numerous forest robin in all (sub-) montane and some mid-altitude forests. Gleans in foliage, flycatches, drops to the ground, snatches off bark and small branches in short flights, at all levels up to the canopy and on sunny edges. In its winter quarters at low
Ecology and biogeography of forest bird communities in Malawi 37
altitude, seen feeding mainly below 2 m, thus occupying much the same niche as Sheppardia gunningi. Birds that remain at high altitude however feed more in the upper strata and few can be mistnetted from March to August. Always attends ant swarms when they pass in or near its territory. Common throughout its range, with 5—10 pairs/10 ha. In winter quarters at Kalwe seven individuals were caught along 200 m of net-lines in five days. Breeding range: 1400-2450 m in the north, 1200-2300 m south of 14°S (down to 1000 m on S Mulanje). Its absence from mid-altitude forest in the north seems related to the presence of Sheppardia gunningi, and it must be excluded by that species on Choma Mt (1750 m). Three birds on the S Viphya (1600 m) were tested in October with tapes of S. gunningi song and reacted aggressively.
A partial altitudinal migrant: a ringing study undertaken by Dowsett (1982) on SW Nyika (2150—2200 m, 32 ha of forest with c. 50 pairs plus non-breeders) showed that females (adults and immatures) departed after breeding; those staying include territorial males and some of the immature males (n = 19 and 7 respectively caught between mid- March and August). The latest adult female was seen on 11 March, attending fledglings. From many observers, first records at low altitudes are in the last week of December or in early January. The species is widespread from January to August in many lowland forests, also in semi-evergreen thickets (e.g. Lower Shire). Still a few seen in September (e.g. foot of Mulanje Mt at 700 m), with one immature in delayed moult caught on 31 October in Lower Shire (50 m, D.B. Hanmer). Distances involved in this migration are of the order of 20-100 km or more; for example 130 km separate the Nyika breeding grounds from the nearest known winter quarters on the Lake-shore, although Nyika birds could also stop in the mid-altitude Kaningina Hills 115 km distant—these were not visited in winter. On the SW Nyika, between 67 and 78 per cent of adult females (n = 59 ringed) returned each year to the same territory (Dowsett 1985).
Olive-flanked Robin Cossypha anomala. Tables 2, 4. Feeds on the ground, logs and in low shrubs, mostly while hopping, or in hop-runs and short sallies to snatch from bark. A regular attendant at ant swarms. Territories are smaller in dense shrubby growth near streams (down to 0.25 ha, Nyika) than in semi-open understorey with treelets away from water (near 1 ha). Overall densities of 10 pairs/10 ha on SW Nyika and Uzumara, slightly less elsewhere. Its absence from the Misuku and Musisi forests is unexplained in ecological terms. 1600—2450 m in the north; 1000-2300 m on Mulanje Mt, marginally down to 900 m in January—August (NJS, Benson & Benson 1977).
Heuglin’s Robin Cossypha heuglini. Pluriregional. Tables 2, 3, 4. Mainly ground stratum, in dense understorey. Local in rain forest, and usually near a stream. Also in any thicket, riparian vegetation and gardens. 50-1900 m, exceptionally to 2050 m in dry Euphorbia obovalifolia forest on S Nyika (Nkhonjera).
Red-capped Robin Cossypha natalensis. Pluriregional. Tables 2, 3, 4. Hops on ground and logs, and at ant swarms sallies to prey from rocks or low trunks. In very dense to semi- open understorey, rather skulking. The ecological counterpart of C. anomala at lower altitudes. Most numerous in Lake-shore forests, with 1—2 pairs/ha. Also in evergreen and deciduous thickets. 50-1750 m, highly local above 1500 m (Choma Mt in the north, Mangochi Mt in the south). Resident at some places such as the Lake-shore (from observations and ringing data) but status at medium elevations unknown (it is largely a migrant in neighbouring countries: Britton 1971).
Spot-throat Modulatrix stictigula. Montane endemic. Table 2: confined to two of three forests in the Misuku Hills (absent from Mugesse, 1600-1880 m, and not below 1750 m
38 Francoise Dowsett-Lemaire
at Wilindi). Difficult to see, hops on ground in very dense shrubbery. At 1800—1900 m about one singing bird per ha—much more vocal in late rains, February—March, than October. 1750—2000 m.
Spotted Thrush Turdus fischeri. Montane near-endemic. Table 4. Forages in leaf litter on ground and rocks, sometimes making quite a noise when turning and throwing dry leaves around, but on the whole very elusive; the song was heard only in September. Discovered for the first time on Mulanje (Chisongeli on the southeast) and Lisau in September 1983, but could have been missed from other apparently suitable localities visited later (e.g. Chikala). Total numbers in Malawi must be very low: thus a maximum of two pairs and another singer encountered in a day visit to Soche (150 ha); one pair and a singer in a similar area at Lisau. 1200—1700 m. There are some off-season records on Thyolo Mt (March and July, NJS), and one was seen in August on Soche (MGD), but a recent sighting of two birds in August at the foot of Mulanje Mt at 700 m (NJS and T. Roberts) indicates some altitudinal movements.
Orange Thrush Turdus gurneyi. Montane endemic. Tables 2, 3, 4. Pecks in leaf litter and on mossy logs, and takes fruits in the understorey; quickly moves off, and elusive overall. Only one brief sighting near ants by Willis (1985). Generally common in tall and moist forest, with 2—5 pairs/10 ha. On SW Nyika it drops out above 2150 m where the forest becomes more fragmented (and drier), and its density over the gradient is inversely related to that of T. olivaceus; but ascends to 2350 m on the wetter eastern scarp where the forest is continuous. On the S Viphya, small patches on the drier central plateau (1700-1800 m) are largely left to its congener. In central Malawi however, where T. olivaceus is practically absent, it occupies short scrubby forest as on the top of Dedza and Dzonze Mts (common) and even very small patches (2.5 ha on Mlunduni Mt). Occurs in mid-altitude forest only east of the Rift; especially numerous on Thyolo and Mulanje Mts, to local in drier types (e.g. Lisau).
1450-2350 m in the north, 1200-2200 m south of 14°S (to 1050 m on S Mulanje). Mainly resident, with some altitudinal movements: one specimen was collected at 700 m c. 30 km east of Misuku Hills (Igembe Hill, Benson & Benson 1949) in July; several recorded at 1000-1200 m in lowland or riverine forest at foot of Zomba Mt (Belcher 1930), near Thyolo and on Machemba Hill near Mulanje (NJS) in June to August.
Olive Thrush Turdus olivaceus. Montane near-endemic. Tables 2, 3, 4. Hops in leaf litter, turning leaves over vigorously; occasionally picks insects on large horizontal or oblique branches; takes fruits directly from canopy, less often on the ground. At dusk comes to forest edges. Attends ant swarms rather infrequently. Seems to prefer drier types of forest than 7. gurneyi and is rare wherever congener is common: thus only one or two pairs or singers recorded at Misuku, Musisi, Uzumara, Chimaliro, Chamambo, Kawandama in the north, and at Thyolo and Zomba in the south, with a few pairs scattered on upper Mulanje. Common only on S Viphya (forest patches of central plateau, 1700—1800 m) and Nyika where the forest is very fragmented (SW and central plateau 2100—2450 m); does breed in patches as small as 0.5 ha, but no more than two pairs occupy patches of 6—12 ha.
1700—2450 m in the north, 1400-2200 m south of 14°S; with only two records of individuals at lower altitudes in August, both at Mulanje (c. 1050 m, Benson & Benson 1977; 750 m, NJS).
Marginal species. The Cape Robin Cossypha caffra (1200-2800 m, Appendix 3) is widespread in montane scrub and at forest edges; on the high Nyika (above 2150 m) it penetrates small patches of 0.2—3 ha where it keeps separate territories from C. anomala.
Ecology and biogeography of forest bird communities in Malawi 39
The Kurrichane Thrush Turdus libonyanus (from woodland) was found at the forest- woodland (or plantation) ecotone locally to 1650 m (Nthungwa, Dzonze, Ndirande).
SYLVIIDAE
Ten insectivorous species from five genera, six in the genus Apalis. Two (Bradypterus, Camaroptera) live close to the ground, while the foliage-gleaning apalises, Chloropeta and Phylloscopus occupy various levels to the canopy. A maximum of three Apalis spp. coexist locally; there is some geographical replacement between canopy species (chapini and cinerea in the north are replaced by chariessa and melanocephala in the southeast) as well as vertical, altitudinal and horizontal segregation in the trio chapini—cinerea-thoracica; thoracica and flavida, both understorey and edge species, marginally overlap at medium altitudes. A. chariessa has the most specialized canopy niche with lower densities than sympatric melanocephala. Bradypterus, Chloropeta and Apalis thoracica may follow ant swarms for short periods (see also Willis 1986).
Evergreen forest warbler Bradypterus lopezi. (incl. mariae, see Appendix 1). Montane near-endemic. Tables 2, 3, 4. Gleans from leaves and bark, occasionally the ground, in dense shrubby understorey and creeper tangles in deep shade (mostly 0-2 m); avoids grass. May be patchily distributed, according to density of undergrowth or other factors (not understood). In the north, quite common on the Nyika and several of the Viphya forests (especially Uzumara, Kawandama and central S Viphya) with densities of 3-6 pairs/10 ha at 1700-2300 m; but uncommon Misuku, rare at Ntchisi (stream gully at 1500 m), and local at lower levels—down to 1250 m on E Viphya. Its absence from the Mafinga—Jembya—Musisi forests is not understood. Much more evenly distributed in the south, with low numbers only in the dry forests of Mangochi and Lisau.
1150—2450 m (down to 950 m on S Mulanje). There is some altitudinal movement down Mulanje (to 600—700 m) in the dry season (March—August), and one June record from lowland forest east of Thyolo (Nkhonjeni, c. 550 m, NJS).
Mountain Yellow Warbler Chloropeta similis. Montane endemic. Table 2: confined to Nyika. Gleans or snatches from foliage in short hops. In tall submontane forest (20—25 m) prefers edges and mid-stratum thickets in clearings. In low-canopy (8-15 m) montane forest (above 2250 m) feeds at all levels to the tree tops, and very common (1-2 pairs/ha). Also in forest regrowth 1-4 m high. 1950—2450 m.
Yellow-throated Warbler Phylloscopus ruficapilla. Montane endemic. Tables 2, 4. Gleans from foliage, sometimes hovers, mostly in middle and upper strata (8-30 m), occasionally lower. Quite common in some submontane forests (Ntchisi, Misuku: up to 10 singing males/10 ha), less so in the drier, more secondary types (e.g. Mangochi) and locally absent (S Viphya, central Malawi). Only in the moister types of mid-altitude forest in the south. Status unclear on Bangwe, may have become extinct through forest clearance (recorded in 1981, not 1983).
1400—2350 min the north, 1200-1950 m south of 14°S (down to 900 m on S Mulanje), with some altitudinal and inter-montane movements. A wanderer (singing) at 1200 m on the E Viphya, below Chamambo, on 25 September 1982 (pers. obs.) was 80 km from the nearest population (Chimaliro). Wanders down to 600—700 m at the foot of Mulanje in January—September (pers. obs., NJS), and to lowland forest near Thyolo (1000-1100 m) in February—August (NJS).
White-winged Apalis Apalis chariessa. Eastern endemic. Table 4: confined to the southeast, in some lowland and all mid-altitude forests. Gleans from leaves and twigs in the canopy and at edges, with a preference for light-foliaged, wide-spreading crowns
40 Francoise Dowsett-Lemaire
(especially Albizia spp.). Densities are highest in the relatively dry mid-altitude Albizia- dominated forest of Lisau (15—18 pairs in 150 ha) but lowest in the wet Newtonia forest of Mulanje (two isolated pairs only in 1983-84, at 1000 and 1300 m) and Chikala. On Thyolo Mt, noted mostly on the lower slopes below 1300 m, and densities of 6—7 pairs/ 100 ha in the lowland Albizia—Khaya forests of the nearby tea estates (1000-1100 m). In the Blantyre Hills more noticeable in secondary forest on the slopes than in mature forest (as on top of Soche). Also in riverine forest at Zomba (1000-1100 m), and at Khonjeni (500-600 m, SE scarp of the Shire Plateau).
500-1550 m. The total Malawi population cannot be much above 100 pairs. Thus one of the most threatened forest birds of eastern Africa, as known from only one locality in coastal Kenya (where perhaps extinct), two forest areas in Tanzania (numbers uncertain) and the small Chiperone Mt in adjacent N Mozambique (Collar & Stuart 1985).
Resident, but the record of a singing male (seen by NJS) on 9 December 1981 at Dzonze, Kirk Range, in a 12-ha patch of Albizia—Khaya forest (1450 m), represents a remarkable example of exploratory movement, across the Rift Valley and 80 km WNW of the nearest regular site (Zomba). We could not trace this individual in a later visit (1983). The forest structure and composition at Dzonze is very similar to that on the Thyolo tea estates where the species breeds, but far too little forest remains in the Kirk Range for a population to become established.
The song (so far undescribed) is a lively, piping duet of four notes repeated in quick succession (at the rate of 6—7 notes/s): tee-lu dee-lu tee-lu dee-lu..., or more rarely the male utters his two notes tee-lu, ..., tee-lu leaving a gap for the female part. Some caution is needed to distinguish these from the 3-note motifs delivered in much the same pitch and tempo by sympatric A. melanocephala (Dowsett-Lemaire 1986).
Black-headed Apalis Apalis melanocephala. Table 4. Feeds like A. chariessa but also frequently in mid-stratum, occasionally lower (as in tangles of creepers). Quite common throughout its range in lowland to submontane forests. Up to one pair or family group per ha (S Mulanje at 1000 m, Thyolo 1000-1400 m). Also in riverine forest at Zomba. 800 m (perhaps to 600 m along the Ruo River) to 1900 m; absent from the Mulanje plateaux except as a wanderer (2200 m, NJS).
Chestnut-headed Apalis Apalis chapini. Montane endemic. Tables 2, 3. In canopy; also on sunny forest edges (down to 2-3 m) and clearings where competes with A. thoracica. Pairs occupy small patches of 0.5—1 ha on SW Nyika but overall densities of 3 pairs/10 ha in more continuous forest (2000-2200 m). Similarly common in several other tall submontane forests in the north (especially N and S Viphya, 1600-2000 m), but local with very small numbers in the secondary forests of central Malawi. Has bred on Chongoni Mt (Benson 1937) but not located in 1983; several on Chirobwe Mt (at the southern limit of its range) even in low canopy (15 m) on ridge at 2000 m. Though it is to a large extent vertically segregated from A. thoracica, countersinging between the two species is extremely frequent and has been noted in all of the many localities of sympatry in northern and central Malawi.
In NW Malawi, competes for the forest canopy also with A. cinerea which it dominates or excludes only above certain altitudes. There is altitudinal segregation in the Misuku Hills, with chapini above c. 1700 m. In the broken forests of the Mafinga Mts (1600-1800 m) chapini is clearly outnumbered by cinerea; at Jembya (1850-1920 m) and Musisi (1700-1800 m) they occur side by side, frequently countersinging. On SW Nyika, they overlap at 1950-2150 m, with chapini dominant above 2050 m; at 2000 m, some pairs keep separate territories, countersing and chase each other. It is significant that at Misuku,
Ecology and biogeography of forest bird communities in Malawi 41
Mafinga and Musisi chapini is not found much below 1700 m, whereas it descends to 1100 m in the Kaningina Hills and to 1170 m on the E Viphya where cinerea does not occur.
1100-2300 m north of 14°S, 1550—2000 m in central Malawi. Largely resident, with some altitudinal movements: thus one pair and two males singing in Mzuma Forest (lake- shore) at 600 m in June, 20 km east of the nearest population on the scarp of the S. Viphya. The very small numbers found in some isolated forests suggest inter-montane move- ments: e.g. one pair on Choma Mt (7.5 ha), 4 km from the nearest other patch; one pair and one or two males on Chipata Mt (44 ha), 32 km from Ntchisi.
Grey Apalis Apalis cinerea. Montane near-endemic. Table 2. In canopy and upper mid- stratum, and on edges; also in lower storeys where A. thoracica is absent (Musisi, Jembya, Mafinga) and in forest regrowth a few meters high in the Misukus. On SW Nyika occupies small patches of 0.5 ha at 1925 m (where chapini is excluded), with densities of c. 3 pairs/ 10 ha at c. 2000 m (with some territories defended against chapini); becomes rare above 2070 m. Countersinging with chapini was noted at Nyika, Jembya and Musisi (1700-2050 m). In the Misuku Hills is almost totally excluded from forest by its congeners: in Mugesse Forest (where thoracica is absent, 1600—1880 m) cinerea occurs below 1700 m in all forest strata and in secondary growth; in Wilindi—Matipa (where thoracica is present) confined to secondary growth below and (locally) along the forest edges. But clearly outnumbers chapini in the Mafinga Mts (1600-1800 m). 1450 m (riparian forest foot of Mafinga Mts and in Misukus) to 2150 m.
Bar-throated Apalis Apalis thoracica. Montane near-endemic. Tables 2, 3, 4. In understorey and mid-stratum of tall forest, up to 16—18 m; but occupies all levels in short. scrubby montane forest (8-15 m tall) as on high Nyika, above c. 2250 m, and Dedza and Mulanje Mts (above c. 2000 m) where it is the only Apalis warbler present. Partial to edges, also in adjacent secondary growth 3-4 m high. Countersings frequently with the canopy/edge species A. chapini in all areas of overlap, but it is not clear how competition affects densities—both are very common side by side over most of their sympatric range of 1550-2300 m. Competes more clearly with A. cinerea (which descends to the lower storeys) and both are largely allopatric (Table 2), with horizontal segregation in the Misuku Hills (see above); only on SW Nyika do they coexist, between 1950-2150 m, with cinerea remaining in canopy.
Densities and altitudinal distribution vary with race. A. t. murina (Misuku Hills, also Tanzania) is widespread, though not numerous, in Wilindi—Matipa but absent from Mugesse forest 8 km distant. There are no records from the Mafinfa Mts apart from a single specimen collected in 1937 (Benson 1940: 622); this noisy bird was certainly absent from all larger forest patches examined in December 1982 and October 1986 (i.e. 132 ha, over half the total forest area). Its absence also from neighbouring Jembya and Musisi, as well as Mugesse, may be related to competition with A. cinerea (see above). 1700-2050 m.
Race youngi (Nyika, N and S Viphya) is numerous throughout, with densities of c. 10 pairs/S ha where forest is fairly fragmented (Nyika 2150-2450 m, S Viphya 1600-1800 m). Overall range 1600-2450 m, with some unmated males wandering a few km away into the edge of pine plantations (Nyika) and small pockets of forest in miombo woodland (Viphya).
Race whitei (central Malawi, also Zimbabwe). Unlike northern races, this one is thriving also in mid-altitude rain and riparian forests (Dzalanyama to Kirk Range); densities of 8—10 pairs/S5 ha on Dedza (2150 m), Mlunduni (at 1800-2000 m) and at
42 Francoise Dowsett-Lemaire
Nsambi (graveyard relict, 1250-1350 m), and over 10 pairs/40 ha of lowland forest at Thambani (1100-1200 m). However, it is probably on the verge of extinction in the Ntchisi area, as absent from Ntchisi Forest itself (for no obvious reason, whole forest explored at different seasons by myself and other observers), and a few birds known only from small patches of drier mid-altitude forest at Chinthembwe Mission (1400 m, a few km from Ntchisi) where the remaining forest is gradually being cleared (NJS and R.D. Medland). 1100-2150 m.
Race flavigularis (southeast). Common on Zomba and Malosa Mts (1400-1950 m), and Mulanje Mt (1000—2400 m) with altitudinal movements down the latter to 600-700 m in January—August (some birds seen in pairs, and keeping vocal contact).
Yellow-breasted Apalis Apalis flavida. Pluriregional. Tables 2, 3, 4. In rather secondary forest types (at any level to canopy), local in mid-altitude rain forest (mostly in tangles under broken canopy, stream gullies and near edges). Also in riparian forest and woodland, evergreen to deciduous thickets, and deciduous forest. 50-1650 m (not above 950 m on S Mulanje). Marginally overlaps with A. thoracica in mid-altitude forest (Kirk Range, Zomba slopes), lowland and riparian (Dzalanyama, Thambani), 1100-1650 m.
Bleating Bush Warbler Camaroptera brachyura. Pluriregional (GC). Tables 2, 3, 4. Pecks tiny prey in foliage of shrubs and herbs, vegetation debris and the ground, usually below 2 m. In submontane forests only in the north and at Namizimu—Mangochi: either very local inside forest (Uzumara, Ntchisi), or within a short distance of the edge (Misuku), but more or less throughout in Jembya—Mafinga—Musisi in the absence of Bradypterus lopezi, and in the dry forests of Namizimu—Mangochi (where B. lopezi is local). More evenly distributed in mid-altitude and lowland forests. Also in any thicket, woodland (where some rank grass) and gardens. 50-1900 m, below 1750 m south of 14°S.
Marginal species. The Cinnamon Bracken Warbler Bradypterus cinnamomeus (1300-2800 m, Appendix 3) is common in montane scrub and bracken, and at forest edges, penetrating some small patches on the Nyika above 2150 m, mostly in herbaceous understorey not occupied by B. Jopezi (for aggressive interactions, see Dowsett-Lemaire 1983d). The Yellow Warbler Chloropeta natalensis is also frequent in montane scrub and bracken (to 2300 m, overlapping with C. similis on the Nyika), and at forest edges in south- central highlands, even in low scrubby forest locally (Kirk Range). The Brown Parisoma Parisoma lugens (1400-1925 m, Appendix 3) is confined to canopy of forest edge Acacia abyssinica where these form small groves of secondary forest. Two Sylvia warblers are migrants from the Palaearctic, the Garden Warbler S. borin common in evergreen forest at all altitudes (to 2300 m) and the Blackcap S. atricapilla mostly above 1500 m (to 2250 m); both take fruits in canopy and smaller trees (Dowsett-Lemaire 1988b).
MUSCICAPIDAE
Nine insectivorous species of six genera: Batis (3), Platysteira, Elminia and Trochocercus mostly in understorey; Muscicapa (2) and Terpsiphone in more open situations. The three Batis are completely allopatric; there is limited altitudinal overlap between the two Muscicapa, and almost complete segregation between Trochocercus (lowland) and Elminia (montane). Batis capensis, Elminia albonotata and Muscicapa adusta have been seen attending ant swarms on a few occasions.
Dusky Flycatcher Muscicapa adusta. Pluriregional. Tables 2, 3, 4. On edges of forest and large clearings, or in broken canopy where there is plenty of space to flycatch; also snatches insects off foliage. Quite widespread, but pairs are widely scattered, though territories can be small (1—2 ha). Also in miombo woodland, riparian forest, edge of
Ecology and biogeography of forest bird communities in Malawi 43
plantations. From 750 or 900 m to 2200 m. A partial altitudinal migrant down to 50 m (Lower Shire) in April—August.
Ashy Flycatcher Muscicapa caerulescens. Pluriregional. Tables 2, 3, 4. Same niche as previous species with very limited overlap at two localities: Thambani (1100-1200 m) and Chipata Mt (1400-1500 m, with caerulescens on edges only, adusta in canopy). Also in riparian forest and woodland, edge of deciduous to evergreen thickets. 50-1500 m.
Cape Batis Batis capensis. Montane near-endemic. Tables 2, 3, 4. Widespread, the most common forest flycatcher above c. 1400 m. Its absence from Mangochi and Namizimu Mts and Dzalanyama may be due to isolation. At all levels of the understorey, occasionally up to the canopy, and on edges. Snatches prey off branches and under the leaves in a short hop or flight, sometimes in the air within 1-2 m of the perch; also pecks on bark while perched, as when taking small insects fleeing up trunks above ants. Some territories are as small as 0.3 ha on SW Nyika (with much edge habitat) but overall densities in tall forest are of 10 pairs/10 ha in most localities.
From 1150 m (1000 m on S Mulanje) to 2450 m, with altitudinal movements down to 800 m at Mulanje in February—August, some birds seen in pairs. On the Nyika, very few ringed individuals wander after breeding, up to 2.6 km (Dowsett 1985).
Forest Batis Batis mixta. Eastern endemic. Table 2: confined to Misuku Hills. As for
previous species, but not noted in canopy. Widespread in all Misuku forests, 1600—2050 m.
Woodwards’ Batis Batis fratrum. Table 4. In understorey (1-18 m) and at edges. The Malawi Hills forests hold well over 100 pairs, with about 10 pairs/10 ha in the more luxuriant part of the forest along and below the ridge, lower densities elsewhere. Also in semi-evergreen thicket in the Lower Shire (Lengwe, very rare). 50-940 m.
Black-throated Wattle-eye Platysteira peltata. Tables 2, 3, 4. Snatches insects off foliage, in a hop or short flight, sometimes in mid-air. At all levels up to the canopy, but more skulking and much less vocal than Batis spp., so densities are uncertain. Largely separated from Batis capensis by altitude, and overlaps marginally at Ntchisi (1350-1400 m, but Platysteira rare), Kirk Range (c. 1300 m, in graveyard relicts), Chikala (at 1350—1400 m, below that only Platysteira), Zomba (slopes, 1400 m), Lisau, and Ndirande (1400-1500 m). Also in riparian forest, (semi-) evergreen thicket, and perhaps wandering into gardens (Nkhata Bay). 50-1600 m (below 900 m on S Mulanje).
White-tailed Crested Flycatcher Elminia albonotata. Montane endemic. Tables 2, 3, 4. Hops along branches in a zig-zag fashion, fanning tail, and catches insects on the wing in jerky flights close to foliage and bark, or in small gaps of understorey. At all levels, occasionally up to the canopy. Densities of 5—10 pairs/10 hain several submontane forests in the north (SW Nyika, Misuku, parts of N and S Viphya but not Kawandama—too cold and exposed?—where rare). Not quite so numerous in the south, though not uncommon in some moist mid-altitude forests. Not noted below 1300 m on Thyolo Mt, nor below 1400 m on Malabvi (only on the moist ridge), and absent from Lisau (1300-1450 m, presumably too dry). Its absence from Ntchisi may be due to isolation, but its absence or rarity (if missed) on Musisi Hill (close to Jembya and Nyika) is not understood.
1200—2450 m (down to 1050 m on S Mulanje). Largely resident (on the Nyika a few ringed birds wander up to 2.5 km after breeding: Dowsett 1985), with some altitudinal movements to 600—700 m at Mulanje in January—August (pers. obs., NJS) and recorded at c. 1100 m in lowland forest near Thyolo (Johnston-Stewart 1982) and Zomba (Belcher 1930, pers. obs.) in May—September.
aa Francoise Dowsett-Lemaire
Blue-mantled Flycatcher Trochocercus cyanomelas. Pluriregional. Tables 2, 3, 4. Much the same feeding techniques as last species, but not as demonstrative and rapid, fanning tail less widely (sometimes not at all); occasionally picks insects from branch as hops along. In thick understorey and liane tangles usually below 8 m; often patchily distributed as confined to denser parts of undergrowth, but quite common in the fairly impenetrable Lake-shore forests (at Kalwe, at least 10 pairs/10 ha). Approaches Elminia albonotata on E Viphya (1200-1400 m, but both species are rather local and do not have overlapping territories), and is segregated by altitude elsewhere: thus below 1200 min the Kaningina Hills (Elminia at c. 1300 m), on lower slopes of Thyolo Mt below 1250 m (Elminia above 1300 m). Also in (semi-) evergreen thicket. 50-1400 m, usually below 1200 m (and below 950 m on S Mulanje).
Paradise Flycatcher Terpsiphone viridis. Pluriregional. Tables 2, 3, 4. Flycatches from a perch or snatches prey off the foliage while hovering, occasionally fans tail along branches like an E/minia. Often in gaps, on edge of mid-stratum thicket, and very patchily distributed. Also in any woodland, thicket, riparian forest and gardens, where more common than in rain forest—e.g. present on the Lake-shore, but outside forest. 50-2000 m, irregular to 2150 m on SW Nyika (i.e. a few pairs in some years and not others, thus likely to be under-recorded elsewhere in one-season surveys). Largely a breeding migrant at medium and high altitudes—e.g. from late September to March on the Nyika.
Marginal species. The Slaty Flycatcher Melaenornis chocolatina is widespread at edges of submontane forest (1600-2200 m, Appendix 3), and may feed a little way inside (to c. 50 m from edge) as when following army ants. Two woodland Batis may come to forest edges: Chinspot Batis B. molitor rarely so, Mozambique Batis B. soror in several places. The White-tailed Blue Flycatcher Elminia albicauda, found normally at margin of riparian forest, thicket, and dense woodland, was seen in forest interior at two localities where E. albonotata is absent: Musisi (1720 m) and Dzalanyama (1550 m), but both in June visits, and the situation in the breeding season remains unknown.
MALACONOTIDAE
Five insectivorous species of three genera—Malaconotus olivaceus also takes fruit, and Laniarius aethiopicus small vertebrates. Of the two Laniarius, aethiopicus penetrates forest only locally and where fuelleborni is absent. The two Malaconotus overlap at one site where they are segregated vertically. Dryoscopus is almost throughout below 2000 m but is even more common in woodland.
Southern Puffback Dryoscopus cubla. Pluriregional. Tables 2, 3, 4. Gleans from foliage and twigs, mostly in the canopy. Territories of 4-8 ha on SW Nyika (at 2000 m) and S Viphya (1700-1800 m), and similarly common elsewhere. Also in any woodland and . thicket. 50-2050 m, with a few pairs to 2200 m on SW Nyika, but not above 1500 m on Mulanje Mt.
Fiulleborn’s Black Boubou Laniarius fuelleborni. Montane endemic. Table 2. Foliage and bark gleaner in dense understorey (up to 16—18 m) of tall forest, also in canopy of low montane forest (8-15 m), at edges and in forest regrowth 34 m high; attends ant swarms occasionally without leaving dense vegetation. Some territories of 0.6—1 haon SW Nyika and S Viphya where forest is very fragmented (i.e. edge habitat important); overall densities in continuous forest of 2—3 pairs/10 ha—except in the Misuku Hills where it is unevenly distributed, i.e. absent from Mugesse, local in Wilindi, not uncommon in Matipa with increasing altitude. 1170-2500 m.
Ecology and biogeography of forest bird communities in Malawi 45
Tropical Boubou Laniarius aethiopicus. Pluriregional. Tables 2, 4. In the north, absent from rain forest except on the Lake-shore (thickets in the understorey); throughout the tather secondary (sub)montane forests of central Malawi (not reached by L. fuelleborni). Silent birds were occasionally seen feeding in the canopy of some tall forests in the south (Chikala, Soche), where more usually at edges. Also in forest regrowth, any thicket, _ Tiverine vegetation and gardens. 50-2200 m (locally to 2300 m on the Nyika, in montane scrub).
Many-coloured Bush Shrike Malaconotus multicolor. Pluriregional (GC). Tables 2, 4. A foliage gleaner in the canopy and mid-stratum (especially in leafy tangles of lianes) of fairly tall forest, mostly at medium altitudes. The only submontane forest where a breeding population is established is on SW Nyika, which may be unique in having a dry season (May—October) completely free of mist and drizzle and thus relatively warm. Territories there are of 6—10 ha per pair (2000-2200 m).
1900—2200 m in the north, and 1050—1600 m in the south (but down to 800—900 m on S Mulanje). On the Nyika and at the foot of Mulanje individuals wander a few kilometres to forest patches where they do not breed; there are records of single birds calling in the Misuku Hills (one in Wilindi in October 1982, where a male had been collected in October 1972: Dowsett 1973), on Mangochi Mt (one male collected in June 1936 by C.W. Benson and one singing in October 1983), and Chikala (June—July 1981, NJS), suggesting fairly wide-ranging and perhaps regular movements of 60-100 km or more from breeding centres.
Olive Bush Shrike Malaconotus olivaceus. Montane near-endemic. Tables 3, 4. At all levels of the forest and on edges, but in the 30 m-tall Newtonia forest on S Mulanje keeps to the understorey, with M. multicolor in the canopy (this is the only locality where these two congeners meet). Quite common in some submontane and montane forests (Mulanje, Zomba—Malosa, Dedza area, Kirk Range), even where rather scrubby (Dedza, Dzonze), although absent from secondary submontane forest on Chiradzulu Mt (perhaps too dry). Only locally in mid-altitude forest, in some of the moister types (Mulanje slopes, graveyard relicts of 2—3 ha in the Kirk Range). 1300—2200 m, down to c. 1000 mon S Mulanje (Ruo Gorge).
Marginal species. The Grey-headed Bush Shrike Malaconotus blanchoti, from wood- land, is found locally in light canopy of secondary forest, or at edges, at medium altitudes (e.g. Ntchisi, Dzalanyama, Kirk Range, up to 1600 m).
PRIONOPIDAE
Only marginal. Parties of two woodland species, the White Helmet Shrike Prionops plumata and especially the Retz’s Red-billed Helmet Shrike P. retzii, frequently foraged in canopy of Malawi Hills forest, in August (not December).
STURNIDAE Only one true forest species, in the north.
Waller’s Chestnut-winged Starling Onychognathus walleri. Montane endemic. Table 2. Has a mixed insect-fruit diet (Dowsett-Lemaire 1988b), and tree chameleons (Cha- maeleo goetzei) are also brought occasionally to nestlings. Forages in foliage of canopy, on lichen-covered branches (hopping and pecking), also flycatches from tall trees. Descends into understorey mostly when the canopy is disturbed by wind. Twelve pairs bred in 160 ha of forest on SW Nyika (2150—2200 m) when feeding conditions were good (Dowsett-Lemaire 1983c); even then these birds were outnumbered by non-breeders and
46 Francoise Dowsett-Lemaire
it seems the number of suitable nest-holes is a limiting factor. Is confined to areas of tall submontane forest in excess of 170 ha and with fairly continuous canopy. 1600-2220 m. Resident, with pairs or groups wandering locally to fruit trees (Misuku, 1450 m, in Trichilia dregeana) and small patches (Nyika) up to 10 km from nearest breeding site.
Violet-backed Starling Cinnyricinclus leucogaster. Pluriregional. Tables 2,3, 4. Highly local in evergreen forest, and numbers vary from year to year. Feeds much like previous species (on insects and fruits in canopy), also at edges and sometimes descending to the ground outside forest. On SW Nyika (2100-2200 m) c. 30 pairs occupied nest-holes in 130 ha in 1980, but none bred in 1981 (a few flocks present) when fruiting of several tree species aborted in dry weather. Also in miombo and other woodland, deciduous forest and thicket. 50-2220 m. A breeding migrant, present mostly from September to March—April.
Marginal species. The Red-winged Starling Onychognathus morio (rocky hills) and Slender-billed Chestnut-winged Starling O. tenuirostris (which breeds on rock faces along montane streams, 1200-2400 m, Appendix 3) occasionally stop over in forest canopy to take fruits (Dowsett-Lemaire 1983c, 1988b).
NECTARINIIDAE
All species have a mixed arthropod-nectar diet. Small insects and spiders are taken by poking and gleaning or hovering in front of foliage and vegetation debris, also by flycatching. Flowers are probed for nectar directly (frontal method) or by piercing the corolla laterally; in two well-studied species (Nectarinia mediocris, N. verticalis) and probably all forest sunbirds, the nectar diet appears unspecialized, in contrast to that of longer-billed species of montane scrub and Protea grassland (Dowsett-Lemaire 1989a). Four Nectarinia (one rather local in forest) and one Anthreptes; up to three Nectarinia coexist in the north, with some vertical and altitudinal segregation—and they differ markedly in their breeding seasons (Chapter 7).
Collared Sunbird Anthreptes collaris. Pluriregional (GC). Tables 2, 3, 4. Locally in broken canopy and liane tangles, more often on edges. Quite widespread below 1700 or 1800 m (though curiously absent from Lake-shore forests) but never numerous. Also in riparian forest and woodland; and various types of thicket. 50-1900 m, not above 1400 m on Mulanyje.
Little Purple-banded Sunbird Nectarinia bifasciata. Pluriregional. Table 2. Not normally in rain forest, except on the Lake-shore (in canopy), 500—700 m, where perhaps it excludes Anthreptes collaris. In riparian forest and various types of thicket (50-1300 m).
Eastern Double-collared Sunbird Nectarinia mediocris. Montane endemic. Tables 2, 3,4. One of the most numerous birds of upland forest. In all levels of foliage but more often in canopy and on edges. Territories of 0.2—0.5 ha on SW Nyika in fragmented forest, and at least 2 pairs/ha in continuous forest in most localities. 1300 m (Kirk Range) or 1400 to 2450 m, down to 1100 m on S Mulanje (though absent from other mid-altitude forests in the southeast). Largely resident; a few birds noted at c. 1000 m and 700 m respectively at foot of Zomba (June) and Mulanje Mts (January)}—Benson & Benson 1977.
Olive Sunbird Nectarinia olivacea. Pluriregional (GC). Tables 2, 3, 4. Common and practically throughout below 1900 m in the north, and 1800 m south of 14°S. In all strata but more often in understorey than N. mediocris. Both share the nectar of many flowers (Acanthaceae shrubs, Achyrospermum, Ipomoea), often piercing narrow tubes. Unlike other sunbirds, olivacea does not seem to have well-defined territories, and precise
Ecology and biogeography of forest bird communities in Malawi 47
densities are unknown. Also in some riparian forests and dense (semi-) evergreen thickets. 500—2000 m (below 1800 m on Mulanje Mt), with few breeding irregularly on SW Nyika at 2050 m and wandering to 2150 m.
Green-headed Sunbird Nectarinia verticalis. Pluriregional (GC). Table 2. In the upper strata of forest (canopy, tangles in mid-stratum under broken canopy) and on edges. Rather patchily distributed and much less numerous than either N. mediocris or olivacea. 1400-2100 m, breeding some years at c. 2200 m on SW Nyika, but avoids the colder and wetter forests of E Nyika and locally absent from parts of the Viphya Plateaux. Subject to local wandering (Nyika, see above; on S Viphya flies over pine plantations to visit isolated forest patches).
Marginal species. Two sunbirds of montane scrub and grassland (Appendix 3), the Greater Double-collared Sunbird N. afra (1900-2500 m) and Bronze Sunbird N. kilimensis (1250—2350 m), often visit forest edges for particular flowers, the latter also some canopy trees, but afra is repeatedly chased by its sibling mediocris (Dowsett- Lemaire 1989a). Two other sunbirds of woodland and scrub, the Miombo Double- collared Sunbird N. chalybea and Yellow-bellied Sunbird N. venusta, visit more locally some canopy trees for flowers.
ZOSTEROPIDAE
Yellow White-eye Zosterops senegalensis. Pluriregional. Tables 2, 3, 4. Foliage gleaner at all levels to the canopy and on edges (for insects, spiders, some fruits and nectar). Throughout all forest types, and locally the most numerous species—e.g. 26 breeding adults netted in 3 ha of forest patches on SW Nyika. Also in forest regrowth, riparian vegetation (thicket, forest), miombo woodland and gardens. 50-2200 m, up to 2450 m on Nyika.
PLOCEIDAE
Dark-backed Weaver Ploceus bicolor. Pluriregional. Tables 3, 4. In mid-stratum and canopy where pecks small invertebrates from bark (on big branches where hops or hangs upside down) and in foliage tangles, probing vegetation debris. Common in lowland and mid-altitude forests, penetrating only locally into submontane forest (below 1700 m). Also in semi-evergreen thicket (Lower Shire). 50-1700 m. Its absence from the north may be due to the rather poor development of the forest canopy at low and medium altitudes.
Marginal species. The Thick-billed Weaver Amblyospiza albifrons, a local marshland weaver, is anon-breeding visitor (dry season) to the interior of some mid-altitude forests, up to 1500 m. The Baglafecht Weaver Ploceus baglafecht and Bertram’s Weaver P. bertrandi (1900-2450 m and 1000-2200 m respectively, Appendix 3), mostly insectivo- rous, are frequent at forest margins and in clumps of trees and scrub. The Spectacled Weaver P. ocularis is widespread at edges (often near streams) at all elevations to 2200 m. Several parties of the woodland insectivore Red-headed Weaver Anaplectes melanotis foraged in forest canopy in the Malawi Hills in August—not December.
ESTRILDIDAE
Only two small species in the forest interior, somewhat segregated by altitude and ecology. Seed-eaters, partial to Gramineae (also Acanthaceae, Euphorbiaceae, Rosaceae, Urticaceae in the case of Cryptospiza: Dowsett-Lemaire 1988b).
Red-faced Crimsonwing Cryptospiza reichenovii. Montane endemic. Tables 2, 3, 4. In low understorey (usually below 4 m) keeping to dense shrubby thickets and herbaceous tangles, often near streams. Scattered breeding territories of 14 ha on SW Nyika
48 Francoise Dowsett-Lemaire
(2150-2200 m), with local wandering in the off-season (up to 3 km for a ringed bird), but fairly elusive, and densities elsewhere uncertain. Drinks frequently; its apparent absence from some submontane forests (Mangochi, Kirk Range) may be due to lack or scarcity of permanent streams. 1500-2300 m north of 14°S (not in montane forest sensu stricto), 1200—2200 m in the south (down to 900 m on S. Mulanje).
Red-throated Twinspot Hypargos niveoguttatus. Pluriregional. Tables 2, 3, 4. In dense herbaceous understorey in lowland forest, more often near edges at medium altitudes. Overlaps with Cryptospiza in Misuku Hills (1600—1800 m), Ntchisi (where latter rare) and in several mid-altitude forests of the southeast where it is to some extent segregated horizontally. Also in deciduous and evergreen thickets. 50-1800 m (below 1000 m on S Mulanje).
Marginal species. The normal habitat of the Green Twinspot Mandingoa nitidula is edges of forest and thicket (never seen far in); widespread at 50-1800 m though not throughout, wandering exceptionally to the Zambian Nyika at 2150 m. The Swee Waxbill Estrilda melanotis (800-2400 m, Appendix 3) feeds at edges and in montane grassland, sometimes in forest clearings. The Red-backed Mannikin Lonchura bicolor visits locally the forest canopy (e.g. Lake-shore) from nearby woodland or thicket. The Magpie Mannikin L. fringilloides comes in to take seeds of the irregularly-fruiting bamboo Oreobambos buchwaldii (e.g. E Viphya, Ntchisi).
FRINGILLIDAE
Oriole Finch Linurgus olivaceus. Montane endemic. Table 2. Takes small seeds from inflorescences in the canopy, liane tangles below canopy gaps, and on edges (e.g. Geranium); hops along lichen-covered branches picking tiny fragments (insects?). Appears very uncommon in Misuku Hills and E Nyika, and erratic at Uzumara, since throughout and in full song in November 1982 (several dozen pairs) but apparently absent in June 1983 and November 1986. Also wanders to S Nyika (Nkhonjera, June), c. 20 km from eastern forests. 1600—2100 m.
Marginal species. Two montane Serinus (Appendix 3), African Citril S. citrinelloides (700-2400 m) and Streaky Seed-eater S. striolatus (1600-2400 m) from scrub, bracken and riverine growth, are found at times taking seeds on edges, the former in canopy (e.g. Hagenia), and the latter low down as well as in narrow riparian forest with dense understorey.
Chapter 7. BREEDING SEASONS
Breeding seasons—as number of clutches started each month—are documented in Table 5 for 64 species (all forest stenotypic birds in Malawi for which we have information, and some of the ecological transgressors). In Tauraco spp. and Muscicapa adusta most records are from evergreen forest; for Indicator variegatus, the woodpeckers Campethera abingoni and Dendropicos fuscescens, the starling Cinnyricinclus leucogaster, Zosterops senegalensis and Hypargos niveoguttatus only forest data have been taken into account. Sources of records are occupied nests, females caught in laying condition or with an early brood patch, observations of dependent fledglings (the majority of data for robins and flycatchers were obtained in that way and backdated to month of laying), courtship feeding in some flycatchers (indicative of laying in Elminia, of laying and incubation in Batis), nest-building and freshly completed nests in a few cases (such as the November record for Coracina caesia, and October-November ones for Apalis chariessa). Of a total
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49
Ecology and biogeography of forest bird communities in Malawi
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52 Francoise Dowsett-Lemaire
of 1408 records, 1000 (71 per cent) come from our 3-year Nyika study (1979-82: Dowsett & Dowsett-Lemaire 1984); 123 recent data from throughout the country (114 obtained by myself, nine by other observers); the remainder are from Benson & Benson (1977, and references therein) and were collected over several decades, at various localities.
For most of the 64 species considered in Table 5, breeding cycles last from (6—) 8 to 12 weeks from egg-laying to independence of juveniles (Dowsett-Lemaire 1983a, 1983b, 1983c, 1985a; many unpublished observations, also Maclean 1985). Raptors and hom- bills are excluded, as their nesting cycles are considerably longer and months of egp- laying are not known in the majority of cases. In both Bycanistes spp. and Tockus alboterminatus there is much feeding activity at holes in October and November, indicating egg-laying takes place in the dry season (two Tockus broods from Nyika were backdated to August clutches). |
Despite the inclusion of data for 32 species that were not in the Nyika sample (either absent there or breeding not documented) and consideration of other localities for those birds already studied on the SW Nyika, the pattern of seasonal variation in egg-laying activity is clear, with a definite peak in October-November (60 per cent of all records) similar to that obtained with the Nyika sample alone (60 per cent for the same months). Overall, 86 per cent of records fall in the period September to December, and 51 of 64 species breed essentially or wholly then—i.e. late dry season when temperatures are rising, and early rains. Exceptions are the two Dendropicos woodpeckers and their parasite Indicator variegatus (dry season only, probably in relation to the annual cycle of wood-boring insects), the two Estrildidae (late rains or dry season when many herbs are seeding), two of three Nectarinia sunbirds, Smithornis (mid-rains), and Chloropeta similis of short montane forest and edges (late rains). More information is needed for Nicator, Alethe choloensis, Ploceus bicolor and Platysteira peltata.
The frugivores Columba arquatrix and Tauraco spp. breed during the September—November peak of fruit availability (Dowsett-Lemaire 1988b). Turacos still raise young in January—February, at a time when most C. arquatrix have left the country. This can be explained by differing fruit preferences: unlike C. arquatrix, turacos are very partial to the abundant crops of Syzygium spp. which ripen in the rains—one such late brood of T. schalowi was raised largely on Syzygium and Rapanea fruits (S Viphya).
Within the bulbuls, Andropadus milanjensis and nigriceps (partly frugivorous, and rather generalized insectivores) breed earlier than Phyllastrephus flavostriatus and placidus (more specialized bark- and ground-feeding insectivores which find more food in the rains). Within the Turdidae, the generalist Pogonocichla starts breeding a month before Alethe fuelleborni and Cossypha anomala—which feed more exclusively on or near the ground and breed once the rains break. Within the warblers, Bradypterus lopezi of the ground stratum also breeds in the rains, starting later than foliage-gleaning Apalis thoracica. There are interesting differences between the seasons of the three Nectarinia species, not apparently related to nectar availability (Dowsett-Lemaire 1989a) but probably to their particular arthropod diets.
Single broods seem to be the rule. The fairly extensive seasons overall in Pogono- cichla and Batis capensis (five months long on the Nyika alone, the Batis February records being from elsewhere) might suggest that some pairs attempt to raise a second brood, but this is not proven so far. In Batis all post-October clutches of individually-known birds on SW Nyika were replacements, and up to three clutches could be laid by some females after successive failures (Dowsett-Lemaire 1985a). In the Nyika 3-year study, double- broodedness was strongly suspected in three Pogoniulus leucomystax in the same season and one second clutch—later abandoned—was laid by an Onychognathus walleri.
Ecology and biogeography of forest bird communities in Malawi 53
Benson (1940) once caught a female Turdus olivaceus accompanying a juvenile, which was about to relay (December, Nyika). There are no other known examples of double- broodedness in the Malawi forest avifauna. One likely exception is Nectarinia mediocris, with a 7-month season on Nyika; its sibling N. afra from montane scrub is able to raise two to three broods (Dowsett-Lemaire 1988c). The rather scattered records for the seed- eating Turtur tympanistria and Cryptospiza reichenovii come from different sites and could be related to geographical variation in food supply.
With the predominance of the Nyika sample, and the fact that Benson did not always publish localities of breeding records, it is difficult to analyse possible geographical variations in breeding seasonality. However, it seems that some species start breeding a little earlier in the south, and this is probably related to the earlier start of the rainy season - there. Thus some or all seven October clutches of Cossypha anomala are from Mulanje Mt (cf. Belcher 1925) whereas Nyika birds (48 records) do not start laying before November when the rains set in. The earliest laying date for Phyllastrephus flavostriatus (September) comes from Thyolo Mt also in the south (Vincent 1935). The only August clutch of a green turaco is of T. livingstonii on Mulanje Mt (Benson & Benson 1947). Turtur tympanistria may have a more restricted season at high altitudes than elsewhere: three Nyika clutches are from August (one) and September (two); there as well as on the N and S Viphya Plateaux (above 1600 m) the song is heard mainly from mid-August to October.
In Smithornis capensis, the November—February laying data are from low altitudes (below 1400 m), but the alarm-behaviour of pairs noted in December (Mafinga Mts), January (Nyika) and February—March (Misuku) indicates reproduction takes place also in the rains in submontane forest, at 1600-2050 m. In the mistletoe specialist Pogoniulus leucomystax, laying as late as December is exceptional on the Nyika (two records, in a year when the favourite mistletoe Englerina inaequilatera fruited later than usual, until January), and the three January records are from Misuku (two) and Mulanje where the mistletoe floras largely differ. The most abundant Loranthaceae of the central highlands (Dedza to Kirk Range) is Phragmanthera usuiensis, fruiting in the late rains, and it is probably significant that no nest with young (easily detected in this noisy species) was found in my November visits there.
Phyllastrephus cerviniventris is the only bulbul with April—May records: the one from May at least is known to come from lowland forest (Lake-shore, Benson 1942) whereas two October clutches are from 1600-1700 m (Mangochi and Mafinga Mts). Finally, the aseasonal June record for Platysteira peltata is from the floor of the Lower Shire valley (c. 50 m, Benson & Benson 1977: 255).
Some generalities on the seasonality of breeding in tropical forest birds—such as the avoidance of the second, heavier half of the rainy season (Moreau 1950)—have already been examined (Dowsett & Dowsett-Lemaire 1984). In view of the complex and varied feeding requirements of individual species, attempts at further generalizations are of limited value. Comparison within species or genera remain difficult as samples from other African regions are usually very small (e.g. Brown & Britton 1980, Serle 1981). The most important source of data for African forest birds now is the study of Brosset & Erard (1986) in northeast Gabon, although precise monthly samples of occupied nests have not been published for all species. Even near the equator rainfall in the Guineo—Congolian Region is unevenly distributed around the year (White 1983a) and breeding activities of Gabon forest birds are still (overall) remarkably seasonal.
54 Francoise Dowsett-Lemaire
Chapter 8. BBOGEOGRAPHICAL POSITION OF THE MOUNTAINS OF MALAWI
There are some important faunistic differences between regions in Malawi, but before these are examined it is useful to place the country in its African context.
Patterns of distribution within the Afromontane archipelago have been discussed for plants (White 1978, 1981, 1983a, 1983b, Dowsett-Lemaire 1989b), butterflies (Carcas- son 1964) and birds (e.g. Moreau 1966, Dowsett 1971, 1986, Dowsett-Lemaire & Dowsett 1989); all of which groups show a high level of endemism in the Region as a whole. Despite the often great distances between mountains, the endemic montane floras and faunas present a remarkable uniformity throughout the Region, i.e. a large proportion of the species are widely distributed. The montane forest avifauna totals some 140 species (Dowsett (1986) lists about 160, but c. 20 are not endemics and also occur in lowland forest). Of these, 38, almost a quarter, are present in Malawi.
Based on faunistic similarities, the mountains of Africa have been grouped into seven regional systems independently by Carcasson (1964, butterflies) and Moreau (1966); their boundaries are fairly similar and also approach those defined by phytogeographers (White 1978, Dowsett-Lemaire 1989b). Moreau’s northern and southern limits of the Tanzania—Malawi group have been altered by Dowsett (1986), who tentatively placed southeast Malawi and adjacent Mozambique within the Southeastern group (Zimbabwe to South Africa), whereas Stuart & Miller (Ms) would treat that area as a separate, though impoverished group.
Table 6 shows the distribution of the 38 montane forest birds of Malawi within the Afromontane Region. Only four species and one incipient species (Phyllastrephus flavostriatus alfredi) are confined to the Tanzania—Malawi group sensu lato (including southeast Malawi); eight (21 per cent) are found in all or all but one group, and a total of 13 (34 per cent) are shared with the very isolated Cameroun system. The high proportion of species (in plants, butterflies and birds) shared between the West and East African mountains, some 2000 km apart, have led some biogeographers to postulate the existence of connecting migratory routes in colder or wetter climatic phases along the edges of the Zaire basin. There is no evidence that the northern route (i.e. northern rim of the basin) has been used in recent times, but relict populations of montane trees (White 1981, 1983b) and birds (e.g. Aplopelia larvata, Bradypterus lopezi, Apalis cinerea) in small forest outliers on the Zaire~Zambezi watershed and other upland areas in western Africa indicate that a southern migratory route may have been used in the not too distant past. An example is illustrated in Fig. 2 showing the distribution of Apalis cinerea in mid- altitude forest away from its montane range. The recent discovery of a small population in northeast Gabon (Bélinga highlands, 1000 m: Brosset & Erard 1986) is of special interest, and one could expect to find more intermediate populations on the many hills of S Cameroun, Gabon and Congo that have yet to be explored. However, the birds of northern Zambia, Angola and Shaba (Katanga) belong to the race alticola, not nominate cinerea of the Cameroun and E Zaire mountains, which suggests that the Cameroun mountains were colonized in an earlier phase, and possibly (though not necessarily) along another route.
Fire protection of Brachystegia plots in northern Zambia has in 30 years induced colonization by forest lianes and trees (Trapnell 1959) followed by the establishment of forest birds, including Apalis cinerea (Madge 1972). In climatic conditions not very different from the present, or when human-induced fires were less frequent, much of the richer miombo woodland of northern Zambia and Shaba could have been evergreen forest.
Ecology and biogeography of forest bird communities in Malawi 55
Fig. 1. Distribution of Apalis cinerea showing montane range (shaded) and mid-altitude stations along the ‘southern migratory route’ (dots). After Stuart (1986) and pers. obs. (Cameroun and Nigeria); Brosset & Erard (1986) (Gabon); Hall (1960), Traylor (1963) and Dean et al. (1988) (Angola); the bird atlasses of Zambia and Malawi (in prep.); Schouteden (1971), Vande weghe & Loiselle (1987) (Zaire, Rwanda-Burundi); Britton (1980) (East Africa).
The groups most species-rich in montane forest endemics are those of the Albertine Rift (just over 80 species), Kenya (c. 60) and Tanzania—Malawi (including the Usambara Mts: c. 56), whereas the southeast highlands (of Zimbabwe to South Africa) are considerably impoverished (some 24 species). Of the 38 species found in Malawi, 35 (92 per cent) are shared with mountains to the north, and only 18 (47 percent) with mountains to the south. Indeed, there is a remarkable dropping-out of species within the latitudes of 9°40—16°30S in Malawi and adjacent northern Mozambique. As many as 20 species (over half the montane forest avifauna) reach their southern, southeastern or southwestern limits of range there (Table 6), against two (Batis capensis, Malaconotus olivaceus) reaching their northern limits. Locations are the Misuku Hills (for Andropadus masukuensis, Modulatrix stictigula), Nyika (Chloropeta similis, Apalis cinerea), N Viphya (Trichastoma pyrrhopterum, Sheppardia sharpei, Onychognathus walleri, Linur- gus olivaceus), S Viphya (Laniarius fuelleborni), Ntchisi Mt (Phyllastrephus flavostria- tus alfredi), Chirobwe Mt (Apalis chapini), Mangochi Mt (Alcippe abyssinica), Mulanje Mt (Pogoniulus leucomystax, Andropadus nigriceps), Thyolo Mt (Phyllastrephus placidus) and nearby Chiperone Mt in Mozambique (Apaloderma vittatum, Alethe choloensis, Cossypha anomala, Bradypterus lopezi, Nectarinia mediocris).
This latitudinal impoverishment is also strongly marked for non-forest montane birds: of 28 species of grassland and forest edges, 15 (54 per cent) drop out through Malawi (Appendix 3). All 28 are present on the Nyika, the largest plateau with over 1000 km? of
Continued on p. 57
56 Francoise Dowsett-Lemaire
Table 6. Montane (near-) endemic bird species occurring in the forests of Malawi, with their distribution in the regional mountain groups of Africa. I = Cameroun—Nigeria; II = Angola; III = Ethiopia; IV = Kenya (Imatongs to Kilimanjaro); V = East Zaire or Albertine Rift (SW Uganda to W Tanzania); VI = Tanzania—Malawi (Usambara to Mulanje and adjacent N Mozambique, a = west of Rift, b = east of Rift and south of 14°S); VII = Southeastern group. ‘/’ indicates species reaching their southern limits within Malawi (or on adjacent Chiperone Mt of Mozambique).
Vla VIb VI
< <
Species 1 eh
Buteo oreophilus
Columba arquatrix Aplopelia larvata Schoutedenapus myoptilus* Apaloderma vittatum Pogoniulus leucomystax Dendropicos griseocephalus : X ; Alcippe abyssinica Xx Xx Xx Trichastoma pyrrhopterum : ; ; Coracina caesia x : x Andropadus masukuensis
A. milanjensis
A. nigriceps
Phyllastrephus placidus
P. flavostriatus alfredi
Alethe choloensis
A. fuelleborni
Sheppardia sharpei ‘ ‘ : 3 f Pogonocichla stellata : : : x x Cossypha anomala
Modulatrix stictigula
Turdus fischeri f :
T. gurneyi X X : T. olivaceus : ; Xx Bradypterus lopezi_ ~ X Xx Chloropeta similis Phylloscopus ruficapilla Apalis chapini é : A. cinerea x x A. thoracica
Batis capensis
Elminia albonotata ; Laniarius fuelleborni x Malaconotus olivaceus ; Onychognathus walleri X Nectarinia mediocris : : Cryptospiza reichenovii X Xx Linurgus olivaceus X
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Ecology and biogeography of forest bird communities in Malawi 57
open habitat, but only nine reach Mulanje Mt, where montane grassland and heath scrub (though floristically diverse) cover less than 200 km’.
Species of lowland forest, by contrast, are far less affected by this latitudinal trend: Apalis chariessa reaches Chiperone Mt (from Kenya—Tanzania), and three species of the Guineo—Congolian forest get as far as the S Viphya (Francolinus squamatus, Nectarinia verticalis) and the Thyolo scarp (Andropadus virens). Batis mixta attains its southwestern limit in the Misukus (its distribution abutting on that of B. capensis) but descends a little further south in Tanzania east of the Lake (to c. 11°S).
In many ways—closer affinities with eastern Africa rather than southern, latitudinal impoverishment—the biogeographical position of Malawi’s montane forest birds shows great similarities to that of montane trees (Dowsett-Lemaire 1989b) and points to similar evolutionary trends in birds and plants.
Chapter 9. REGIONAL AND ALTITUDINAL VARIATIONS IN NUMBERS AND COMPOSITION OF SPECIES
9.1. Variations between regions (North, Centre, Southeast)
From faunistic and floristic characteristics three forest regions can be recognized in Malawi: in the north (9°40—13°20S, 500-2450 m, some 190 km? in toto), centre (14°10—-15°45S west of Rift, 1100-2150 m, just under 16 km), and southeast (14-17°S east of Rift plus the Malawi Hills, 600-2300 m, c. 120 km’). These are inhabited respectively by 86, 56 and 81 bird species (Tables 2, 3, 4 and Accipiter melanoleucus), of resident status or breeding migrants.
The forests of the central region are not only very small but structurally impoverished, and the absence of so many species found elsewhere is not surprising—in particular there is no Alcippe, no Alethe (understorey under broken or short canopy unsuitable for ant- following), no Phyllastrephus flavostriatus, only one Pogoniulus, one local Andropadus, no Phylloscopus. However, there is an empty niche for an Andropadus bulbul on Dedza and Chongoni Mts: the dense low forest on Dedza appears eminently suitable for A. nigriceps, numerous at similar altitudes and higher in fragmented forest on Nyika and Mulanje. Reasons for its absence may be historical (see Chapter 11). A few eurytypic bird species are present in the area in habitats other than rain forest (e.g. Bycanistes bucinator, with only B. brevis in forest). Of the 56 species, 53 (95 per cent) also occur in the north— the three missing are Stactolaema leucotis, Ploceus bicolor, and the montane Malacon- otus olivaceus reaching its northern limit on Chongoni Mt—and 54 (96 per cent) in the southeast—the two missing are Tauraco schalowi, and the montane Apalis chapini occurring no further south than Chirobwe Mt. In terms of Montane (near-) endemic elements, all but one of 17 are shared with forests to the north or to the southeast.
Of 86 forest species found in the north, five are ecological transgressors only marginally in rain forest (confined to the Lake-shore in that habitat, e.g. Centropus superciliosus). If these are excluded, the forest avifaunas of the north and southeast appear equally rich in species, with 63 in common (78 per cent). Differences in species composition seem related to the better structural development and richer flora of forest at submontane levels in the north, and at low and medium elevations in the southeast. Thus the montane component is more important in the first region (34 species) than the other (24, 20 in common), as 11 species reach the southern limit of their range in north-central Malawi and three others skip south-central Malawi to reappear further south (Table 6 above), beyond Zimbabwe. Only four montane birds of the southeast are missing in the
58 Francoise Dowsett-Lemaire
north: the niche of Malaconotus olivaceus is, however, filled there by Laniarius fuelleborni; Alethe choloensis is the vicariant of A. fuelleborni; Turdus fischeri and Coracina caesia are mostly or only in mid-altitude forest.
Several of the montane species confined to the north do not have an ecological counterpart in the southeast—Buteo, Trichastoma, Modulatrix, Andropadus masukuensis, Sheppardia sharpei, Onychognathus walleri, Linurgus. Buteo oreophilus is restricted to the two largest areas of submontane forest (Misuku, E Nyika) at the southern end of a long chain of mountains in East Africa where it is widely distributed (e.g. Turner 1980). Only Mulanje Mtin the south has forest of comparable size to the Nyika, but it may be too isolated to sustain a viable population. The ecological requirements of the other montane birds just mentioned (tall, fairly continuous canopy for Onychognathus, moist, sheltered understorey for most of the others) are not met in the impoverished southern submontane forests. Those montane birds that do have a counterpart in the south are usually replaced there by a lowland form, alethes excepted: Dendropicos griseocephalus by D. fuscescens, Phyllastrephus flavostriatus alfredi by P. f. vincenti, Apalis chapini and cinerea by A. melanocephala, Chloropeta similis marginally by C. natalensis.
The southern forests are richer in lowland elements, in particular Eastern endemics: of 14 species in all, 12 are in the southeast (though Cercococcyx montanus apparently not in forest) versus six in the north. A comparison of the forest structure and avifauna at two major sites of lowland rain forest (N Lake-shore, Malawi Hills) is instructive. The most distinctive features of the Lake-shore forests are a very discontinuous canopy dominated by two or three tree species (mainly light-foliaged Brachystegia) and a moist, tangled understorey; the fruit assemblage is poor, e.g. there are very few figs, and lianes are dominated by four genera of Apocynaceae with hard, mammal-dispersed fruits. By contrast the forest on the Malawi Hills has a more diverse flora, with 25 species of large trees forming a fairly continuous canopy (none clearly dominant, but several species of fig trees, one common) and a sheltered mid-stratum. Of 36 bird species in the first place and 39 in the other, 27 are shared (mostly raptors and understorey species). The faunistic differences can largely be related to the respective floristic and structural features: the Lake-shore forests have no woodpeckers (large trees too scattered and few in species), no Stactolaema barbets (poor fruit supply and few figs) and none of the associated parasitic honeyguides, only one Bycanistes (the Malawi Hills can support two), no bark-feeding Phyllastrephus nor Ploceus bicolor, no Dicrurus and no Batis. But the dense and moist lower storey has Andropadus virens and Sheppardia gunningi with no ecological equivalent in the Malawi Hills—A. virens occurs in wetter forests elsewhere in the south.
At low and medium elevations in the Shire Highlands and on Mulanje Mt, forests are wetter and more luxuriant than in the Malawi Hills and gain in bird species, including Columba delegorguei, Oriolus chlorocephalus, Apalis chariessa and Malaconotus multi- color (all absent from the north except the Malaconotus locally in submontane forest). With one main exception, the mid-altitude forests of the north lack a mature, continuous canopy and resultant sheltered understorey. Ntchisi (mid-altitude plus lower submontane) is the only well-developed forest which, from its floristic characteristics, should in theory be able to support some of these absentees—especially a Stactolaema barbet since fig trees are numerous. But it is the most isolated forest site in the country (Chapter 2.3) and may still be too small (253 ha).
Also related, it seems, to structural features is the fact that a greater proportion of montane forest birds come down to medium altitudes in the south, e.g. among the genera Alethe, Turdus and Phylloscopus (see below).
Ecology and biogeography of forest bird communities in Malawi 59
9.2. Variations along the altitudinal gradient
In the north the greatest number of bird species is observed in submontane forest at 1600—2000 m (67 overall, plus Chloropeta similis appearing near 2000 m) and variations along the altitudinal gradient parallel those in numbers of tree species—.e. trees 2 m high and above, excluding secondary growth. Numbers of bird species vary as follows: 36 at 500—700 m (Lake-shore, 64 tree species); 44 at 1100-1450 m (Kaningina, E Viphya, Chipata, 92 tree species, with a maximum of 38 birds at 1100-1200 m); 42 at 1350—1640 m (Ntchisi, 94 tree species); 67 at 1600—2000 m (Misuku to S. Viphya, Nyika excepted, 216 tree species); 48 at 2050—2250 m (Nyika, 146 tree species); and only 22 at 2250-2450 m (central Nyika, 57 tree species). There is a linear correlation between number of bird ee (y) and that of tree species (x) expressed by the formula y = 17. 3 + 0.23 x (n= 6, r° = 88 per cent, P < 0.01).
In the south, bird species numbers are highest at medium elevations (1000-1200 m on Mulanje, 1200—1400 m in the warmer Shire and Liwonde Highlands). On Mulanje Mt, the only massif with a continuum from lowland to montane forest, the number of bird species rises from 41 at 650—900 m (91 tree species) to 51 overall at 900-1400 m (a maximum of 48 birds at 1000—1200 m, 124 tree species on S slopes), then drops to 32 in submontane forest at 1500—1850 m (97 tree species) and gradually to 20 at 2000-2300 m on the high plateaux (floristic diversity uncertain). Elsewhere, bird species numbers are similarly moderate in lowland forest (39 in the Malawi Hills, 600-940 m, 78 tree species; 42 near Thyolo, 1000—1100 m, flora incompletely known) and highest in mid-altitude forest (62 species at 1200-1600 m, Shire and Liwonde (Chikala) Highlands, 128 tree species, with a maximum of 61 birds at 1200-1400 m). Above 1450 m, numbers start dropping, to 32 species on Malosa—Zomba at 1600—1950 m (81 tree species).
Most of the montane elements of southern Malawi reside in the luxuriant mid-altitude forests (i.e. 20 of 24 species) whereas in the north, many of the montane birds drop out below 1400 or 1500 m (leaving only 10 of 34 species at medium elevations); this loss is only partly compensated for by the appearance of new lowland forms, hence the overall impoverishment.
Table 7 shows the variation in the proportion of montane elements with altitude at 21 major localities of forest in northern and southern Malawi. In lowland rain forest, this varies from 0 (below 900 m) to 10 per cent; in mid-altitude forest (c. 1100—1500 m, lower on Mulanje) from 21 to 31 per cent; in submontane and montane forests (>1500 m) from 47 to 77 per cent, with a local exception on Mangochi Mt (28 per cent)—a small mountain with presumably a warmer microclimate. In northern Malawi, the avifauna of all submontane forests considered together has exactly 50 per cent montane elements (34 of 68 species), but the figure for individual forests is usually higher (Table 7). This is explained by the fact that montane birds are overall more widely distributed than lowland species; indeed 13 montane species are present in all or all but one or two localities of submontane forest (Table 2, e.g. Columba arquatrix, Pogonocichla stellata, Apalis chapini) versus six lowland birds equally widespread (e.g. Tauraco schalowi, Zosterops). The overall proportion of montane elements in the submontane forests of the south is slightly less at the same altitude (44 per cent of some 55 species regular above 1600 m): the latitudinal effect, if any, is more than compensated for by the local impoverishment. of the montane avifauna.
Size and exposure of mountains also influence the altitudinal range of spécies: at similar altitudes, the proportion of montane elements is greater on large versus small massifs (Mulanje vs Zomba and central highlands; Thyolo Mt vs Chikala) and on the rain- exposed, cooler side of mountains (E vs SW Nyika). In other words, montane species
60 Francoise Dowsett-Lemaire ;
Table 7. Proportion of montane elements in forest avifaunas, varying with increasing
altitude. Locality Forest type Alt. (m) No. (%) of Total No. montane birds of species North of 14°S Lake-shore lowland 500-700 0 (0) 36 Kaningina +E Viphya mid-altitude 1100-1400 10 (24) 41 Ntchisi mid-altitude + submontane 1350-1640 14 (33) 42 Chamambo submontane 1600—1800 21 (60) $5) Uzumara submontane 1600—1920 29 (63) 46 Misuku submontane 1600-2050 26 (51) 51 Chimaliro submontane 1850—2000 25 (64) 39 SW Nyika submontane 1920-2220 26 (57) 46 E Nyika submontane 1750—2350 30 (73) 41 C Nyika montane 2250-2450 — 17 (77) 22 South of 14°S Malawi Hills lowland 600-940 0 (0) 39 Near Thyolo lowland 1000-1100 4 (10) 42 S Mulanje mid-altitude 900—1400 16 (31) 51 Thyolo Mt mid-altitude 1170-1450 16 (28) 58 Chikala mid-altitude 1300—1600 10 (21) 47 Mangochi submontane 1550-1700 10 (28) 36 Chongoni submontane 1600-1950 14 (47) 30 Zomba—Malosa submontane 1600-1950 17 (53) a2 Mulanje Mt (sub) montane 1500—2300 22 (69) 32 Chirobwe submontane 1800—2000 16 (57) 28 Dedza (sub) montane 1800-2150 13 (62) 21
descend lower on large mountains, and lowland species ascend higher on smaller (warmer) ones—a fact also widely observed in trees (White 1978, Dowsett-Lemaire 1989b).
The effect of these relief-related climatic factors is illustrated in Table 8 for 21 montane bird species. Of 20 present on Mulanje and other highlands in southern Malawi, 13 occur significantly lower on the former. Responses of birds to environmental factors vary between individual species and, not surprisingly, no two species have exactly the same altitudinal range. Columba arquatrix, Andropadus nigriceps and Turdus olivaceus can be characterized as high montane elements. In several fairly unspecialized passerines, the upper altitudinal level reached is determined by the upper limit of forest (2450 m on Nyika, 2300-2400 m on Mulanje, 2150 m on Dedza): Andropadus nigriceps, Pogo- nocichla, Cossypha anomala, Bradypterus lopezi, Apalis thoracica, Batis capensis, Elminia albonotata, Nectarinia mediocris. But all these differ in their lower altitudinal limits, though the two flycatchers come close; it is believed that Pogonocichla, wide- spread in any type and size of mid-altitude forest in the south, is excluded from that level in the north by Sheppardia gunningi. Turdus gurneyi and Phylloscopus ruficapilla are examples of species common in the moist, tall mid-altitude forests of the south and absent from similar levels in the north. In Apaloderma vittatum and Schoutedenapus myoptilus the upper altitudinal limit is similar to that of tall-canopy forest—2350 m on E Nye in the north, c. 2000 m on Mulanje in the south.
Ecology and biogeography of forest bird communities in Malawi 61
Table 8. Regional variations in the altitudinal range (m) of some widespread montane
forest birds S of 14°S
Species N of 14°S Mulanje Mt Elsewhere Columba arquatrix 1500-2300 1500-2300 1500-2150 Aplopelia larvata 1100-2300 1050—2000 1050-2100 Schoutedenapus myoptilus 16002350 c. 1200-2000 1200-1450 Apaloderma vittatum 1400-2200 1400-2000 1300-1900 Pogoniulus leucomystax 1400-2300 1400—2000 1300-2150 Andropadus milanjensis 1100-2250 1000-1850 1100-2000 A. nigriceps 1600-2450 1500-2300 1600-1950 Phyllastrephus placidus 1100-2000 700/900-1820 1000-2000 Alethe choloensis absent 700/900-1820 1200-1900 Pogonocichla stellata 1400-2450 1000-2300 1200-2150 Cossypha anomala 1600-2450 1000—2300 absent
Turdus gurneyi 1450-2350 1050-2200 1200-2150 T. olivaceus 1700-2450 1600-2200 1400-2100 Bradypterus lopezi 1250-2450 950-2300 1150-2150 Phylloscopus ruficapilla 1400-2350 900-1900 1200-1950 Apalis thoracica 1400-2450 1000-2400 1100-2150 Batis capensis 1150-2450 1000-2300 1200-2150 Elminia albonotata 1200-2450 1050-2300 1250-2150 Malaconotus olivaceus absent 1000-2200 1300-2150 Nectarinia mediocris 1400-2450 1100—2400 1300-2150 Cryptospiza reichenovii 1500-2300 900-2200 1200-2150
Examples of lowland elements occurring higher on smaller mountains include Apaloderma narina (to 1600 m on Ntchisi and Chikala, but 1000 m on the southern slopes of Mulanje and 1250 m on the drier western side) and various passerines—Erythropygia quadrivirgata, Cossypha natalensis, Apalis flavida, Platysteira peltata, Trochocercus cyanomelas, Hypargos niveoguttatus, etc.
In mountain areas where the foothills are directly connected to the Guineo—Congolian rain forest, the number of species increases considerably with decreasing altitude (e.g. in eastern Zaire: Prigogine 1980). On truly isolated massifs, the avifauna of the lower levels is impoverished, and the greatest number of species is observed at medium or submontane elevations (e.g. the Impenetrable Forest in Uganda: Keith et al. 1969, Keith 1980).
9.3. Area and other factors related to species numbers The relationship between the number of species (flora or fauna) and the size of different habitat islands occupied has generated a lot of interest, and controversy in its interpreta- tion (important review by Gilbert 1980; also Higgs 1981, Boecklen 1986). There is increasing evidence that habitat heterogeneity is an important underlying component of the species—area relationship (e.g. Boecklen 1986), although the fact that area and habitat diversity may themselves be strongly correlated (Rafe et al. 1985) has rarely been considered by earlier authors.
The Malawi sample of over 40 forest ‘islands’ provides a unique opportunity to compare the effect of these two factors, and a third (altitudinal range) on bird species diversity. Habitat diversity is expressed here by the total number of tree and woody shrub
62 Francoise Dowsett-Lemaire
species (2 m high and above) as this was the most readily measured variable. As each tree species has its own microstructure, an increase in species numbers reflects an increase in the overall structural complexity of the forest (e.g. in feeding niches for insectivores) and also represents a more diverse fruit assemblage (of direct relevance to frugivorous birds).
For reasons exposed in the above chapters (e.g. important variations in forest flora and avifauna between regions and along the altitudinal gradient), it is best to consider subsamples of forest localities within certains regions and altitudinal limits. Lowland forests are excluded from this analysis as there are too few of them and their avifauna is impoverished.
A preliminary study (after one season) of the breeding avifauna of 89 patches of submontane forest on the SW Nyika (1950—2200 m) showed area (y) to be strongly correlated to bird species numbers (x, Fig. 1 in Dowsett-Lemaire & Dowsett (1984), though the formula should read log y = 1.13 + 0.25 log x,. The regression coefficient differed significantly from zero (P < 0.001) and 7 (square of the correlation factor, expressing the percentage of the variance accounted for by the regression equation) was 83 per cent. A more complete study after three seasons gave
log y = 1.15 + 0.3 log x, (P < 0.001; 7 = 86 per cent)
Tree species were censused in 12 of these patches, all 20-25 m tall, situated within a narrow altitudinal range (2100-2200 m) and varying from 0.2 to 90 ha. Each patch is in grassland, 50-100 m from others. The number of breeding bird species (y) shows a significant relationship with area (x,)
y =4.3 + 10.2 log x, (P < 0.001; 7° = 98 per cent) and also with number of tree species (x,) y =-95 + 62.7 log x, (P < 0.001; 7° = 98 per cent) Floristic diversity and area are themselves strongly correlated log x, = 1.7 + 0.16 log x, (P < 0.001; r° = 98 per cent)
From the similarly high values of r° for both factors, it seems likely that area and floristic diversity are equally important in influencing bird numbers, though their inter-relation- ship calls for caution in this interpretation.
A similar analysis can be extended to the submontane forests of the north above 1600 m (Misuku to S Viphya), excluding Musisi (incompletely surveyed) and E Nyika (as the forests are above the altitudinal limit of several species, and thus relatively “impov- erished’ for their size). At the ten forest localities considered, probably no more than one or two species could have been overlooked (e.g. elusive Sarothrura elegans). Isolation plays a similar role for all, as each site is 15—25 km from its nearest neighbours. The effect of altitudinal range can be studied in addition to that of area and floristic diversity. The number of bird species (y) is related to area (x,) by the following regression equation
y = 10.9 + 11.7 log x, (P < 0.001; 7° = 92 per cent) to floristic diversity (x,) by y = 64.5 + 52.6 log x, (P < 0.001; r = 77 per cent) and to altitudinal range (x,) by log y = 1.05 + 0.24 log x, (P < 0.001; 7° = 83 per cent)
Ecology and biogeography of forest bird communities in Malawi 63
As for the Nyika sample, floristic diversity and area are also strongly correlated log x, = 1.54 + 0.18 log x, (P < 0.001; r° = 76 per cent) and so are altitudinal range and area log x, = 0.96 + 0.53 log x, (P < 0.001; 7° = 85 per cent) and floristic diversity and altitudinal range : x, = 47.6 + 0.22 x, (P < 0.001; 7° = 94 per cent)
High values of 7” suggest all three factors influence bird species numbers; but again, inter- correlations between them call for caution in the interpretation of relationships which in any case are not necessarily causal.
In the central highlands of Malawi, the sample of forests is rather small (n = 7 after excluding the relict, artificially reduced mid-altitude forests), and area is the only factor weakly correlated to bird species number
log y = 1.09 + 0.14 log x, (P < 0.05; r° = 66 per cent)
In the southeast, the analysis is limited to the eight localities of mid-altitude forest, as submontane forests are too few. Area remains a good predictor of bird species numbers
log y = 1.34 + 0.13 log x, (P < 0.005; r° = 80 per cent)
but not floristic diversity (7? = 45 per cent), even though, overall, the greatest diversity in both bird and tree species is observed at medium elevations (Chapter 9.2). It is striking that Thyolo Mt, the single richest forest in birds (58 species) has a much poorer flora (72 tree species) than the middle slopes of Mulanje (124 tree species, 51 bird species): however, the canopy at Mulanje is dominated by pod-bearing Newtonia buchananii and at Thyolo by several Ficus trees. The latter provide an ample food supply and probably explain the presence there of several frugivores (Stactolaema spp., Columba delegorguei) absent from S Mulanje. Other species (e.g. Oriolus chlorocephalus) may be excluded from the Mulanje slopes by the colder microclimate of the ravine forests.
Chapter 10. ENDEMISM AND ISOLATION IN THE HIGHLANDS OF MALAWI
Endemism in the different African mountain systems has been described by Dowsett (1986) and shown among forest birds to be highest in the most isolated Cameroun-Nigeria group (nearly 50 per cent of the species, see also Stuart & Miller, Ms), while it approaches 35 per cent in the E Zaire group. The Tanzania—Malawi group (sensu lato from Usambara south to Thyolo—Chiperone) is the third richest, with 15 endemics (27 per cent): six turdines (Modulatrix stictigula, Dappled Mountain Robin M. orostruthus, Iringa Ground Robin Sheppardia lowei, Usambara Ground Robin S. montana, S. sharpei, Alethe choloensis), four warblers (Apalis chapini, Long-billed Apalis A. moreaui, Mrs Moreau’s Warbler Bathmocercus winifredae, Red-capped Forest Warbler Artisornis metopias), four sunbirds (Banded Green Sunbird Anthreptes rubritorques, Loveridge’s Sunbird Nectarinia loveridgei, Moreau’s Sunbird N. (loveridgei) moreaui, Rufous- winged Sunbird N. rufipennis), and one bush-shrike (Uluguru Bush Shrike Malaconotus alius). Several of the Tanzanian endemics are confined to single large massifs (e.g. Stuart & Jensen 1985), but in Malawi only Alethe choloensis has a fairly restricted distribution, in the southeast and adjacent N Mozambique.
64 Francoise Dowsett-Lemaire
In addition, several well-marked races are endemic to limited areas. Apalis thoracica flavigularis, the most distinctive of four races of this apalis found in Malawi, is confined to Mulanje and Zomba—Malosa; and A. t. youngi to the Nyika and Viphya plateaux. Malaconotus olivaceus also has a subspecies confined to Mulanje and Zomba—Malosa (bertrandi), whereas the makawa race of central Malawi is similar to Zimbabwe birds. Nominate Cossypha anomala is restricted to Mulanje, Chiperone and Namuli Mts in adjacent Mozambique, and the nearest populations of the species are 460 km distant in northern Malawi. The race belcheri of the barbet Stactolaema olivacea (a species montane in parts of its range) occurs on two mountains only (Thyolo and Namuli some 200 km apart) and is greatly isolated from other populations (Dowsett-Lemaire & Dowsett 1987). The nearest conspecifics of the elusive thrush Turdus fischeri belcheri (endemic to southeast Malawi) are in southeast Zaire and Natal, South Africa. The race nyasae of Trichastoma pyrrhopterum (Nyika and N Viphya) is 650 km south of the nearest population in western Tanzania; despite their isolation, these birds produce a group song identical to that of nominate pyrrhopterum and reacted strongly to a tape of Uganda birds (recorded by Keith, in Keith & Gunn 1971) that I played to them.
Of the 30 non-forest species of the Tanzania—Malawi mountain group, three are local endemics with restricted distributions in southwest Tanzania and northern Malawi (Black-lored Cisticola Cisticola nigriloris, Churring Cisticola C. njombe and Mountain Marsh Whydah Euplectes psammocromius). In addition, the forest-edge weaver Ploceus baglafecht and sunbird Nectarinia afra, and one grassland bird, Red-winged Francolin Francolinus levaillantii, have well-marked races endemic to the Nyika Plateau (Benson 1953b) and are isolated to varying degrees—especially the sunbird whose closest relatives are in eastern Zaire and South Africa. The Afro-alpine relict Scarlet-tufted Malachite Sunbird Nectarinia johnstoni nyikensis is probably endemic to the Nyika and is greatly isolated from central and eastern African races (Hall & Moreau 1970). The warbler Bradypterus cinnamomeus, of secondary growth and bracken thickets, belongs to a group of dull-plumaged birds where subspeciation could be hard to notice, but its confinement to Mulanje Mt south of the N Viphya is remarkable (the nearest population is 550 km to the north).
Among the lowland or mid-altitude forest birds, only two have endemic races in Malawi: Francolinus squamatus doni (S Viphya, some 450 km from the nearest locality for the species, in Tanzania) and Sheppardia gunningi bensoni (Lake-shore and Viphyas); the latter is represented by a population widely disjunct from the other two, in coastal East Africa and Mozambique (Hall & Moreau 1970). The song of this robin has evolved into a dialect quite distinct from that recorded in Mozambique (Transvaal Museum Sound Library), but characters of timbre and syntax are close and two Malawi birds tested with the foreign dialect reacted to it as to their own song.
Isolation has not produced phenotypic changes in every species: for example the populations of Alcippe abyssinica on Namizimu and Mangochi Mts belong to the same race (stictigula) as those of northern Malawi, 300 km distant; the same is true for the populations of Andropadus nigriceps of northern and southeast Malawi, separated by 370 km. Coracina caesia, despite some enormous gaps in its distribution, has only two recognizable races over the whole of its African range (Hall & Moreau 1970). Within the Tanzania—Malawi group sensu Dowsett, two thirds of the forest species are represented by asingle subspecies, and only a few by more than two (Dowsett 1980); even in the highly isolated Angolan mountains, several species do not differ subspecifically from popula- tions elsewhere. Dowsett has argued that isolation per se may not necessarily result in
Ecology and biogeography of forest bird communities in Malawi 65
speciation, and this may be especially relevant for resident forest species experiencing relatively little ecological stress.
To sum up, forest birds in Malawi have undergone limited genetic differentiation in an area centred on the massifs of Mulanje and Thyolo, and even less elsewhere. Most of the endemic races relate to isolated populations, but not all isolates show phenotypic change. On the Nyika Plateau, four species of open habitats have endemic races as against one from forest interior, indicating perhaps that genetic change comes more quickly in birds more exposed to ecological stress.
Among forest plants, local endemism in Malawi is extremely low, nearing 1 per cent (for tree species) on Mulanje and less elsewhere (Dowsett-Lemaire 1989b).
Chapter 11. DISTRIBUTION GAPS AND THE ROLE OF COMPETITION AND ISOLATION
“Presumably there are ecological reasons for most local presences and absences, though these may often not be obvious” (Dowsett 1980: 195). When the forest avifaunas of the three regions of Malawi are compared to variations in size and structure of the habitat (Chapter 9), most of the local gaps in species distribution can be explained on ecological grounds. Patchy distribution within a region is often clearly related to the birds’ ecological requirements. For example, Apaloderma vittatum’s niche—sheltered mid-stratum under tall, fairly continuous canopy, within a certain altitudinal range—is not met everywhere, and the bird is absent from or only an occasional wanderer to forests that are too low or scrubby (e.g. Mangochi Mt, most of the central highlands), or where the canopy is too discontinuous, or both (e.g. S Viphya).
Interspecific competition between close relatives may further restrict the range of some species. The montane avifauna in Africa is characterized by a very low ratio of species to genera (about 2 to 1: Table 1 in Dowsett 1986). Even when lowland elements are considered, 43 of 66 genera in the Malawi forests are represented by only one species, and the ratio of species to genera is 1.6 to 1. In the other 23 genera, there is often local exclusion between congeners.
Examples of complete altitudinal replacement are found in Cossypha (anomala and natalensis) and Sheppardia species, and almost complete replacement in the two Apaloderma and Malaconotus spp. Examples of geographical replacement are more common: between the two green Tauraco, the two green Pogoniulus, two Dendropicos, two Alethe, three Batis; and there is only marginal overlap between the two Bycanistes and Stactolaema. The fruit diets of the Tauraco and Bycanistes are reasonably well-known, and overlap considerably (Dowsett-Lemaire 1988b). In only five passerine genera is it normal to find two species side by side, with a maximum locally of three (Andropadus, Turdus, Apalis and Nectarinia) or four (Phyllastrephus). In all of these but Turdus, three species coexist only if at least two are vertically segregated.
The extent to which two close relatives exclude each other altitudinally in parapatry can be demonstrated by the situation in allopatry: thus in the absence of Apaloderma vittatum from the Ethiopian mountain group, A. narina occurs widely in montane forest up to 3500 m (Fry et al. 1988). In the forests of northern Malawi, the number of coexisting Apalis warblers may be influenced by the structural diversity of the forests: three species (A. chapini, cinerea and thoracica) occur side by side (albeit with some altitudinal and territorial replacements) on the SW Nyika and in parts of the Misuku Hills. In the more broken and secondary forests of Mafinga and Musisi, and on Jembya (where the
66 Francoise Dowsett-Lemaire
understorey is unusually open), only two coexist, A. thoracica having given way to A. cinerea—though the former is the heavier of the two (Dowsett-Lemaire 1983d: 369). In the mid-altitude forest relicts on the Zambian plateau, A. thoracica and cinerea are essentially allopatric (Benson et al. 1971).
Territorial replacement and frequent countersinging between these ree Apalis warblers are proof of direct interspecific competition. In other groups of species, one can only suppose that competition is responsible for the dominance of one relative by another: the fact that numbers of Phyllastrephus placidus in northern Malawi are inversely related to those of P. flavostriatus alfredi may also reflect a different response to some environ- mental factor that is not obvious to the observer. And the same comment could apply to the pair Turdus gurneyi-T. olivaceus.
In addition to the factors discussed above, historical reasons, i.e. variations in the extent of forest and in the ways it was recolonized during the climatic vicissitudes of the Quaternary, are likely to be responsible for some of the more puzzling distribution gaps. Ihave already mentioned (Chapter 9.1) that the absence of a generalist Andropadus bulbul (especially A. nigriceps) from the high montane forests of Dedza and Chongoni Mts appears abnormal. Presumably, the reduction in forest cover in a drier phase could have led to local extinction, and present populations of A. nigriceps to the east and north are too far away (150 and 210 km respectively) to permit recolonization.
The absence of five montane passerines from the Misuku Hills (Alcippe abyssinica, Andropadus nigriceps, Phyllastrephus flavostriatus alfredi, Cossypha anomala, Shep- pardia sharpei) seems even more anomalous, since the habitat appears suitable—the forests are of great size, cover a wide altitudinal range from 1600 to 2050 m, and are structurally the most luxuriant and floristically the most diverse in the north (Dowsett- Lemaire 1989b). Moreover, all five species occur on mountains to the north in southwest Tanzania (the Andropadus, Cossypha and Alcippe as near as in the Isoko Hills, c. 22 km distant, Benson & Benson 1949) and to the south. The Phyllastrephus and Andropadus in particular are common in all the other forests of northern Malawi, including the Mafinga Mts 25 km away and in sight of the Misukus. All of these passerines are basically resident, but occasional altitudinal or inter-montane movements are known for the two bulbuls involving distances slightly greater than 25 km. Possibly the joint occurrence in the Misukus of Phyllastrephus placidus and Andropadus masukuensis, both feeding on bark, and the niche expansion of the former into the mid-stratum, hamper recolonization by P. flavostriatus. The fact also that three species (Modulatrix stictigula, Apalis thoracica, Laniarius fuelleborni) are absent from one of the three Misuku forests (720- ha Mugesse), and that the Apalis and Laniarius do not seem to fill all suitable habitat in the other two (especially in Wilindi closer to Mugesse), supports the hypothesis that recolonization of the area is not yet completed. Such process may be extremely slow in species with little dispersal ability (see Chapter 12.3), and the population dynamics of montane forest birds in general are characterized by low breeding productivity and turn- over rates (Dowsett-Lemaire 1985a, Dowsett 1985). Another case in point is Ntchisi Forest, the most isolated patch of fine submontane forest in the country: some of the species present are known to be wide-ranging (e.g. Apaloderma vittatum) and some of the absentees have clearly very limited colonizing abilities (e.g. Elminia albonotata, see Chapter 12.3).
Ecology and biogeography of forest bird communities in Malawi 67
Chapter 12. THE MOBILITY OF FOREST BIRDS
One can recognize three types of movements in the forest birds studied, albeit that in afew cases different strategies can be observed in different populations or individuals of the same species.
12.1. Intra-African migration
As stressed by Dowsett (in press), the subject of intra-African migration is ripe for a comprehensive review. Much scattered literature and unpublished information remains to be analysed in the way a few species have been treated by, for example, Britton (1971, 1973). Benson’s (1982) list of species subject to local movements or migration south of the equator suffers from a number of omissions.
Among the bird species breeding in the Malawi forests, Campephaga flava (Britton 1973), Terpsiphone viridis (e.g. Benson et al. 1971, Benson & Benson 1977) and Cinnyricinclus leucogaster (Traylor 1971) are known to undertake complex migratory movements through south-central Africa, the timing and extent of which often vary in different populations. These are more typical inhabitants of woodland and thicket than forest. The forest-thicket robin Cossypha natalensis is wholly or partly migratory in several parts of its range (Britton 1971) but is resident in at least some areas of Malawi, though the evidence so far is fragmentary. The elusive rail Sarothrura elegans calls only in the rains and is suspected of undertaking some movements, as birds have been attracted to lighted windows at night (e.g. Benson 1957). There is a June record in Malawi, however, and in Natal (one of the species’s headquarters), it is reported in all months (Cyrus & Robson 1980). Benson (1982) also suspected the cuckoo Cercococcyx monta- nus to be a breeding migrant in Malawi (itis never heard in the dry season), but individuals have been caught in June in the south (Benson & Benson 1977: 253) and in Mozambique (Irwin 1981); the situation in East Africa is far from clear (Stuart & Jensen 1985).
Both Bycanistes hornbills wander, singly or in flocks, outside the breeding season; in addition, over 90 per cent of the B. brevis population of the Misuku hills is migratory, leaving each year in mid-rains for an unknown, but almost certainly northerly, destination.
Of the 38 montane (near-) endemic species, only two (Columba arquatrix, Schoutede- napus myoptilus) are clearly breeding migrants, the swift entirely so. Although several African swifts are well-known intra-continental migrants, the case of S. myoptilus seems largely to have escaped attention. In eastern Zaire, interestingly, Prigogine (1966) noticed marked fluctuations in numbers on the edge of the Itombwe massif: from rare or absent in most months, the species suddenly becomes abundant from mid-June to September. In October-November, birds appear to move southwards. In Zimbabwe, most records are from the rains (M.P.S. Irwin in Jitt.). In the little-explored Uzungwa Mts of Tanzania (c. 8°S, 36°E) small flocks have been seen flying over in July and August (Stuart et a/. 1987). It seems likely that, in March—April (at the end of the rains), the Malawi birds move nearer the equator.
In Columba arquatrix, over 90 per cent of the population of the north (perhaps less in the south) vacates the country in December. Returns, in June or August depending on the year, are finely tuned to the fruiting of particular food trees. In the southern Cape, birds move into the forests in their hundreds when Olea capensis fruits massively every 2-3 years (Phillips 1927, pers. obs.). Elsewhere in Africa, this pigeon is thought to range widely between isolated forests, but there is ample scope for study of these movements in relation to the phenology of favourite fruit trees. Fruiting of most tree species in Malawi is strongly seasonal and thus predictable (Dowsett-Lemaire 1985b, 1988b), and this is
68 Francoise Dowsett-Lemaire
true generally of tropical forests with at least one marked dry season. From Malawi, C. arquatrix probably migrate north to forests experiencing a different rainfall regime with, concomittantly, different patterns in the seasonal availability of fruit.
12.2. Altitudinal migration
Altitudinal movements during the non-breeding season have been recorded so far in 25 species, of which 22 are Montane (near-) endemics. The other three include Campephaga flava (see above) in which the movement off the plateau areas is fairly general; Muscicapa adusta, a forest-woodland flycatcher whose populations show a partial altitudinal shift in the winter (cf. Benson et al. 1971, Benson & Benson 1977); and Bycanistes bucinator in at least one high-altitude location (Nyika).
Of the montane birds, Pogonocichla stellata is affected by an important shift of population from January to September throughout Malawi: on the SW Nyika near the upper altitudinal limit, all adult females leave, as well as non-territorial adults of both sexes and many immatures. The situation in the colder and wetter forests of the E Nyika and the high Mulanje plateaux requires investigation. In the highlands of Zimbabwe, all forests above 1300 m are (almost) completely deserted, but the population of Chirinda Forest (900-1200 m) is apparently sedentary (Irwin 1981). In the Midlands of Natal, Oatley (1982) found that territorial males stay