The effects of habitat change on the avifauna of Mount Marsabit forest, Kenya

Abstract

Forests are important ecosystems because of their immense contribution to national economy and the livelihoods of local communities. They are also important for biodiversity conservation and are indeed critical habitats for birds. In Kenya, native forests support 299 of the country's 1079 species of birds. They also provide refuge to 50% of Kenya's 71 threatened bird species. The richness and composition of forest avifauna gives an indication of the importance of the forest for bird conservation. Mount Marsabit ecosystem is a habitat Island (as it is surrounded by desert-like conditions) facing increasing threat to its biodiversity. Despite its protection status it is experiencing drastic human induced changes in land cover both within the park and the surroundings. A steadily increasing population coupled with sedentarisation around the reserve, growing livestock numbers and pumping of water from the mountain to supply Marsabit town are some of the immediate concerns. For proper management, there is need for efficient and effective monitoring. Birds can be used as monitors of ecosystem change. Little quantitative work has been done on the avifauna of Marsabit. The purpose of this study was to assess the structure and composition of the bird communities and how they relate to habitat changes in Mount Marsabit National Park in northern Kenya. The specific objectives were to determine (1) bird species composition, abundance and diversity; (2) habitat utilization by major bird guilds and (3) the vegetation/land cover changes and their effects on the avifauna in the study area. In this study, a combination of standard bird sampling techniques, especially point counts (variable radius circular plot), mist netting and ad hoc species searches were used to survey the avifauna of Mount. Marsabit for six months along habitat gradients. Sampling was done on three fixed transects. It was hypothesized that the distribution, abundance, and diversity of birds on Mount. Marsabit followed altitudinal gradient and that the bird community changes were linked to habitat loss and change. The study was carried out in seven different sites between December 2004 and May 2005. The sites were selected along three large belt transects traversing through major habitats and land use types adjacent to the park. The results of the study indicated that the park is rich in bird habitats and hence bird species. A total of 153 bird species belonging to 43 families were recorded. Most of the birds were resident in the forest but there was clear movement of birds up and down the mountain slope even on a daily basis. Typical dry land species moved up the mountain during the dry season in search of food and water. Large fruit eating birds such as pigeons remained in the forest throughout the study period. Bird densities varied significantly amongst mature forest, degraded forest, open shrubland and farmland habitats. This study added 13 new species to the list of birds known to occur in the area. The endangered William's Lark (Mirafa Williamsi) and the vulnerable Lappet-faced Vulture (Torgos tracheolitos) and Imperial Eagle (Aquila heliaca) were found in the park. In addition, 25 migratory species were recorded. This study has shown that birds can be valuable indicators of the effects of upland forest fragmentation on biodiversity. Protection of Mount Marsabit forest and the associated wetlands is crucial to conservation of birds and biodiversity in general. The study was part of a larger GEF sponsored initiative on the entire mount Marsabit ecosystem, it is hoped that the findings will be useful in the formulation of a sound management plan for the area and form a basis for future monitoring activities.