Factors influencing diversity and abundance of farmland birds around Kakamega forest, Kenya

Abstract

As the human population grows, particularly in the developing world, so does the demand for land for agriculture in pursuit of food security. Over the past three decades, this has resulted in massive degradation, fragmentation and loss of natural habitat with corresponding loss of biodiversity. However, biodiversity conservation and agricultural systems can be complimentary rather than mutually exclusive. On the one hand, there are a range of ecosystem services that are rendered to farmlands by wild flora and fauna, including pollination, seed dispersal, nutrient cycling, soil conservation and genetic exchange. On the other hand, agricultural landscapes offer additional foraging and dispersal opportunities for species from neighbouring degraded habitats. Kakamega forest, Kenya's only tropical rainforest, has been severely fragmented, mainly due to human encroachment for agriculture, leading to degradation of natural habitat for its biodiversity. This study, conducted fsomOctober 2006 to March 2007, aimed at ", assessing structural characteristics of a selection o{,)"arms around Kakamega forest, determining species richness, diversity and density of birds-on the farms and evaluating of the association between bird community structure and these structural characteristics. A total of 30 farms were studied, covering a total of 38.2 ha, selected and clustered into three strata based on relative proximity to the forest. Farm structure was characterized in terms of size, hedge. length and volume, vertical and horizontal habitat heterogeneity, density of woody plants, the type of cash crop grown, proportion of crop cover, plant diversity and distance from the forest. Birds were surveyed five times using the Distance sampling procedure along line transects.