Effects of forest edge on pest control service provided by birds in fragmented temperate forests

Abstract

Controlling herbivorous insects by insectivorous birds is one of the most important regulating services in forest ecosystems. The fragmentation of forests and the associated increase of edge effect, however, influences forest bird communities and thereby may have an impact on biological control via the modification of prey-predator interactions. In the present study we aimed to examine how insectivorous bird abundance and their predation on artificial caterpillars were affected by forest edges and vegetation structure in fragmented temperate forests of southwest Hungary. We found an unexpected negative humpedshaped pattern for predation rate as well as for bird abundance, having peaks both at the edge and in the interior (50 m from the edge). We found a positive correlation between bird abundance and predation rate, therefore the important role of birds in insect pest control was supported. Interestingly, the abundance of insectivorous birds had negative relationships to forest structure variables, such as tree basal area and tree species richness. This unexpected pattern may be a result of the context-dependency of edge effects that cannot be fully explained by our study. It highlights the need for more studies to explore the general pattern of edge effect on insect pest control.