Evidence for an Edge Effect on Avian Nest Predation in Fragmented Afromontane Forests in the Bamenda-Banso Highlands, NW Cameroon

Abstract

Habitat loss and fragmentation in tropical areas have long been presumed to reduce avian nesting success due to increased predation rates. Nevertheless, this prediction remains largely untested in tropical areas, because empirical data on the impacts of forest fragmentation on nest predation at both the landscape and patch scales in the tropics are still scarce, especially in West Africa. In this study, we examined the edge effects on nest predation rates in a large montane forest block and small forest fragments. Artificial nests used for our experiments mimicked the real nests of passerines confined to montane forest undergrowth in the Bamenda-Banso Highlands, the Northwest region of Cameroon, an endemic bird area of high conservation priority. We found equal overall predation rates in the landscape dominated by the large forest block as well as in the landscape consisting of small forest fragments, implying that the probability of nest failure was not significantly affected by habitat fragmentation on a landscape scale. However, predation rates were higher close to forest edges in the small forest remnants. Since such remnants represent the majority of local montane forests, this result suggests that the edge effect on bird nest predation may reduce nest survival and the population viability of many range-restricted bird species confined to the remaining natural habitats of the Bamenda-Banso Highlands.