Effects of forest cover and fragmentation on bird functional guilds in understorey birds in shade coffee habitats of southwest Ethiopia

Abstract

Habitat loss and fragmentation, as consequences of anthropogenic land use changes, are the main drivers of global biodiversity loss. In this study, we evaluate the response of functional guilds in forest understorey bird communities to the amount of forest cover and fragmentation in shade coffee habitats of southwest Ethiopia. Bird functional guilds were classified based on forest dependency (forest specialists, forest generalists, open-habitat specialists) and specific dietary requirements (insectivores, frugivores, nectarivores, granivores and scavengers). Birds’ abundance was determined using mist-nets in 10 sites. Within a kilometre radius from the centre of each bird-trapping site, the amount of forest cover and fragmentation metrics were determined using FRAGSTATS. We used a generalised linear model to evaluate the relationship between the abundance of bird functional guilds with the amount of forest cover and fragmentation level. The abundance of the understorey bird community as a whole increased in line with the amount of forest cover and decreased with fragmentation. Abundances of bird functional guilds showed variable responses to the amount of forest cover and fragmentation: forest specialists, frugivores, insectivores and granivores increased with the amount of forest cover and decreased with fragmentation for the former three guilds. Generalists, open-habitat specialists and nectarivores did not show significant responses either to the amount of forest cover or to fragmentation. Our study demonstrated that the majority of bird functional guilds respond positively to the amount of forest cover and negatively to forest fragmentation. In particular, many guilds in understorey bird communities require extensive amounts of forest cover and contiguous forest habitat to survive.