Species richness and community composition of songbirds in a tropical forest-agricultural landscape

Management strategies that attempt to mitigate tropical biodiversity loss require detailed studies of biodiversity in different land-uses. In this study the community structure and species richness of songbirds was characterised along with the vegetation structure, in three land-use types in and around a tropical forest reserve in Uganda (intact, mature forest; regenerating secondary forest; smallholder agriculture). Each land-use type had 30-35 count stations that were sampled twice by means of a 15-min recording session. In total, 118 bird species were recorded from 192 station counts. Number of species/station was similar in intact and regenerating forest and lower in smallholder agriculture. Songbird communities in intact forest were highly distinct from those in smallholder agriculture and were composed of forest-dependent species. Communities in regenerating forest were intermediate between intact forest and agriculture, although much closer to intact forest. Generalised Linear Model (GLM) modelling revealed that tree density and distance to the nearest intact forest had strong positive and non-linear effects on the community composition and forest species richness of songbirds. Simulations using these models showed that agroforestry programmes would not raise tree densities to levels that would shift agricultural songbird communities towards forest communities. Current and bestcase agricultural practices are therefore unlikely to contribute to the conservation of the songbird component of forest biodiversity in this area.