A comparative study of the forest avifauna of Mount Elgon National Park
That the only montane forest in eastern Uganda exists on Mt. Elgon (Katende et al 1990) is important in light of the fact that some West African and some South African bird species reach their eastern and northern limits at Mt. Elgon (Granvic 1923).
The avifauna of Mt. Elgon is well known, although many of these previous records are from Kenya (Granvic 1923). Therefore, there remain many bird species that await confirmation as to their existence in Uganda, while some species are as yet unrecorded for Mount Elgon National Park. Avifaunal communities very often provide a good indication of changes within an environment. Many species are indicative of habitat in which they live and a great deal of information can be derived from the composition of avifaunal communities.
A study of the forest avifauna was conducted in the upper montane forest at 2850 metres. Two study sites, located approximately 3.2 km from the Piswa Patrol Hut, were designated disturbed and undisturbed forest. The two sites were approximately 1 hectare in size. The disturbed forest had been intensively grazed until 1983 and had been only lightly grazed since. At this low-gradient site, the trees formed a closed canopy, dominated by Afrocrania volkensii, a species restricted to the Afromontane region that was fruiting at the time of this study. The understorey vegetation was 1-2 m in height, dominated by the woody herb Mimulopsis alpina and the ground layer was dominated by Pilea tetraphylla.
As reported by the Park Rangers, the other site was undisturbed forest due to its steep gradient, characterised by sparse tree cover, a dense 2-3 m shrub layer, dominated by Mimulopsis alpina and the bamboo Arundinaria alpina and a sparse ground layer. The undisturbed site had a a small stream running through it.
A combination of mist netting and timed species-count techniques were employed to sample the avifaunal composition at the two study areas. The two methods were performed separately on alternate days.
A total of eight, six meter long mist nets were erected at each site. All the nets were opened at approximately 08:00 and closed at approximately 18:00. The length of time the nets were open varied, depending on rainfall. When open the nets were checked every 30-45 minutes. To prevent a decline in catch rate, the nets were moved to a new location within the study area every 2-3 days. Each net was 4 m in height and therefore, only sampled the understorey birds. When captured, the birds were identified, weighed, measured and photographed before being released.
Mist netting sampled only birds in the ground strata. Therefore timed species-counts were employed to sample birds representing the wider forest community. To reduce the over-representation of conspicuous species, a list of birds within 20m of the observer and a full list were recorded (Pomeroy and Tengecko 1986). This technique was carried out at the same study sites in all weather conditions. A one hour count was made at both sites four times a day. Auditory and visual identification was used to record the birds.
A bird species list was compiled from these observations, including species identified from reconaissance trips at lower altitudes.
Of the thirteen species captured in mist nets, two were caught in the disturbed forest only. Both White-throated Greenbul, Phyllastrephus albigularis and Uganda Woodland Warbler, Phylloscopus budongensis are known to be dense forest specialists (Britton 1980; van Perlo, 1995). A further seven species were caught in both the disturbed and undisturbed forest. The most frequently caught birds were the endemic race of White-starred Forest Robin, Pogonocichla stellata elgonensis, distinguished by the absence of yellow margins on the outer tail feathers (Keith et al 1992), Olive Thrush, Tardus olivaceus, Yellow White-eye, Zosterops senegalensis senegalensis and Streaky Serin, Serinus striolatus. The Mountain Yellow Warbler, Chloropeta similis, White-eyed Slaty Flycatcher, Melaenornis fischeri and Abyssinian Crimsonwing, Cryptospiza salvadorii were less frequently captured inhabitants of both forest sites. Birds indicative of the undisturbed forest groundstrata were Abyssinian Ground Thrush, Zoothera piaggiae, Brown Woodland Warbler, Phylloscopus umbrovirens, Mountain Illadopsis, Illadopsis pyrrhopterum (another forest specialist), and Oriole Finch, Linurgus olivaceus. All the species captured during mist netting typically represented the undergrowth avifauna.
The timed species-counts increased the list of species encountered as they included a greater range of species such as raptors which soar above the forest and above the net level. This method added another three species to the disturbed forest species list. These were Rufous-chested Sparrowhawk, Accipiter rufiventris, Mountain Buzzard, Buteo oreophilus and Olive Pigeon, Columba arquatrix. A further eight species were observed in the undisturbed forest area comprising Lanner Falcon, Falco biarmicus, Scaly Francolin, Francolinus squamatus, Hartlaub's Turaco, Turaco hartlaubi, Forest Wood-hoopoe, Phoeniculus castaneiceps, White-headed Wood-hoopoe, Phoeniculus bollei, Yellow-billed Barbet, Trachyphonus purpuratus, Brown-backed Scrub Robin, Erythropygia hartlaubi and White-browed Sylvietta, Sylvietta leucophrys, another inhabitant of the groundstrata.
The most striking and spectacular birds in the Benet grasslands were Black and White-casqued Hornbills, Ceratogymna subcylindricus (that were displaying), Long-crested Eagle, Lophaetus occipitalis and Verreaux's Eagle, Aquila verreauxi. Other species frequently seen comprised Speckled Mousebird, Colius striatus, Common Stonechat, Saxicola torquatus axillaris (a partial migrant that breeds at higher altitudes and disperses to lower areas in the non-breeding season) (Pomeroy 1989), Common Robin-chat, Cossypha caffra, Hunter's Cisticola, Cisticola hunteri, Northern Double-collared Sunbird, Nectarinia pressi, Golden-winged Sunbird, Nectarinia reichenowi, Olive Sunbird, Nectarinia olivacea, a pair of scavenging White-necked Ravens, Corvus albicollis, Black-crowned Waxbill, Estrilda nonnula and two races of Baglafecht Weaver, Ploceus baglafecht reichenowi and Ploceus baglafecht stuhlmanni living side by side! Individuals of the two races were observed in the heathland and the Benet grasslands. Races reichenowi and stuhlmanni were very distinctive in the field, providing the added bonus of being able to compare both the adults. The adult males of the race reichenowihad a small black eye patch that extended down the cheek and a black nape, neck and mantle. The rest of the face was ochre yellow. The females had a black face, crown, nape, neck and mantle. There was no yellow above the moustachial stripe, only on the chin. Females were very similar to the males and females of the race stuhlmanni. However, the latter had a grey-brown nape, neck and mantle.
Species identified between Kapchorwa and the Benet grasslands
Evidence that Elgon supports a great variety of birdlife is supported by a number of lowland forest bird species that were observed during our trek to Piswa. The lower forest provided sightings of Eastern Bronze-naped Pigeon, Columba delegorguei, White-crested Turaco, Turaco leucolophus, Black Saw-wing, Psalidoprocne pristoptera, Common Bulbul, Pychonotus barbatus, Brown-chested Alethe, Alethe poliocephala, White-bellied Black Tit, Parus albiventris, Tacazze Sunbird, Nectarinia tacazze, Pied Crow, Corvus alba and Black-headed Waxbill, Estrilda atricapilla.
This survey revealed a number of intriguing observations.The most remarkable finding was the observation of two races of Baglafecht Weaver, Ploceus baglafecht, perched in the same area of scrub.The adults of the two separate races were distinguishable in the field.There are eight known races of Baglafecht Weaver, Ploceus baglafecht, all distributed within Africa (Howard and Moore 1984). Race reichenowi inhabits Kenya and northern Tanzania whereas race stuhlmanni ranges from eastern Zaire and western Tanzania to southern Uganda. It may be possible that the distribution of two intermediate forms of the Baglafecht Weaver, Ploceus baglafecht, overlaps at Mt. Elgon. If this was the case it may be good evidence that Mt.Elgon lies at the distributional limits of two distinctive subspecies.
Although Uganda Woodland Warbler, Phylloscopus budongensis,has previously been recorded for Mt. Elgon (Wilson 1995) it is regarded as an endemic species to the Central African highlands (Vande Weghe 1992).
Lanner Falcon, Falco biarmicus, a northern migrant, and Long-crested Eagle, Lophaetus occipitalis, were the only species recorded during this study which needed confirmation (Wilson 1995).Another finding was the presence of two specialist forest species in disturbed forest only and many generalist forest species found in both undisturbed and disturbed forest habitats. One may predict that the two specialist species would have a smaller distribution than the generalist species and would conform to the hypothesis that generalist species may be more widely distributed than specialist species (Pomeroy and Ssekabiira 1990).
The composition of Mt.Elgon's birdlife emphasises the richness and uniqueness of its environment. Conservation of such an environment is important in terms of preserving its invaluable ecological communities.
This survey of montane forest birds revealed only the presence or absence of species in the study areas. Very little data exists about montane avifaunal communities and their ecology, with the exception of altitudinal distribution (Vande Weghe 1992). One can only speculate that differences in the forest avifaunal composition might be due to the consequences of human activities in the area. However, no conclusive evidence was derived from this study to reveal differences that may exist in the avifauna between the undisturbed and disturbed forest habitats.
It is necessary to understand the negative effects of local human activities on Mt. Elgon's environment and to develop measures in an attempt to reduce them. There is an urgent need to collect more information about ecological forest communities and it is hoped that further research will do so and aid in future conservation.
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Katende, T., Ipulet, P., Rodriques, R. and Dranzoa, C. (1989) Birds and woody perennials inventory, Mount Elgon Forest Reserve. Sustainable development and forest conservation in Uganda, Technical Report No. 1.
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Pomeroy, D. and Tengecko, B. (1986) Studies of birds in a semi-arid area of Kenya. III The use of timed species-counts for studying regional avifaunas, J.Trop.Ecol., 2, 231-247.
Vande Weghe, J.P. (1992) Distributional ecology of montane forest birds: ideas for further research, Proceedings of the VII Pan-African Ornothological Congress, 469-474.
Wilson, S.E. (1995) Bird and mammal checklists for ten national parks in Uganda, National Biodiversity Data Bank, Kampala.
Project co-ordinator: Stephen Kings
Field work team: Stephen Kings and Sabila George Paul
Project advisor: Mr. R. Kityo, Makerere University Zoology Department, Mr. P. Doyle.
Report Writer: Stephen Kings
This study was followed up in 1997 by Caroline McParland and Opus Otuko Joseph Charles: Avifauna species richness and diversity in Mount Elgon National Park, Uganda