Comparative study of bird guilds in different cropping systems on farm lands adjacent to Kakamega forest

Abstract

Tropical rainforests are characterized by habitat stability and complexity. Hence, the forests support a rich biological diversity, including 40% of all bird species. However, these rain forests have been shrinking due to increasing rate of deforestation, fragmentation, and other forms of resource exploitation. Degradation and loss of rainforests has threatened their rich biological diversity and the life-support systems. However, the rate at which birds are displaced by forest clearing and the potential for birds' conservation on farmlands are not well understood. This study sought to establish the role of farmlands adjacent to tropical rainforests in birds' conservation. The study was carried out for the period of seven months (September 2010-March 2011) in small scale farms lying between two forests (Kakamega main and Kisere) in Kakamega County, Kenya. The objectives were to determine the cropping systems in farmlands adjacent to Kakamega forest determine the spatial and temporal variability of birds' habitats in Kakamega, assess the relative abundance of birds found in different cropping systems in the study area and to determine the variability in the community structure of bird guilds in the study area. Information on crop cover types, crop growth stages and estimates of percentage cover was obtained. Data on bird species composition, diversity, richness and abundance in the identified habitats were collected through timed species counts, conducted in a circular plots of 35m radius. Individual birds were counted, identified and classified into feeding guilds. Their foraging sites were also noted by crop cover and flight height levels present at the sampling sites. Sampling of birds was done twice a week and crop growth stages were evaluated twice a month. Three major habitat types (sugarcane farms without trees, sugarcane farms with trees and farms with mixed crops) were identified. A total of 17,397 birds belonging to 126 species were found in all habitats. Bird species richness was variable among the various cover types while species diversity remained relatively stable (Shannon diversity' H'=3.1 and H'=3.5). There was difference (X2=6, df=5, p < 0.05) in number of birds in different bird guilds, insectivorous having the highest number while the nectivorous contained the lowest number. Similarly, the birds showed preference for top height level than the middle and the bottom levels (X2=3, df=2, p < 0.05). Birds utilized various crop stages opportunistically and hence monthly differences were not significant (dmax P > 0.05). Farmlands in the study area hosted a rich community of birds, some of which utilized the adjacent tropical rainforest. It was also found that farmlands provided refuge for displaced species and the presence of indigenous trees and fruits appeared to offer favorable feeding and breeding opportunities. Bottom height level was, however, unstable because of the manipulations by the land owners. Nevertheless, this study showed that the mixed farming landscape in Kakamega offered ample potential for birds' conservation provided that key habitats remain stable and are enriched with tree crops