Forest edges and habitat selection in birds: A functional approach

Abstract

Edge effects encompass a complex panoply of biotic and abiotic phenomena across woodland borders. I identify four main explanations which have been proposed to explain avian habitat selection with respect to forest edges: 1) individualistic resource and patch use, 2) biotic interactions; 3) microclimate modification and 4) changes in vegetation structure. 1) relates nest site location in woodlands relative to the edge to the proximity of food resources. It is shown that, all other things being equal, birds which are wholly dependent on resources found within woodlands will tend to avoid forest edges. Woodland species dependent upon resources found in adjacent habitats will tend to be found near to edges to enable their exploitation. 2) identifies competition, predation and brood parasitism as factors which have the potential to influence bird habitat selection near edges. 3) identifies microclimate modification as a potential influence which may act directly on nesting success or indirectly through its effects on food supply; 4) relates the activities of birds, such as nesting, feeding or use of song posts, to vegetation structure and/or floristic composition at the edge. Research on edge effects of birds in woodland has provided few practical recommendations to conservation managers. Forest edge management needs to take into account the multiple cause and effects which influence habitat selection at the edge and to target species of conservation concern.