Avian responses to forest edges have received much attention in recent years, particularly because of the potential effects of deforestation on the quality of remaining forest patches. However, individual birds' responses to forest edges are more often inferred than observed, and most studies of space use emphasize territory placement, with little or no detail on within-territory movements. Thus, our understanding of the effects of edges on movements of forest birds remains limited. We recorded movements of 85 winter flocks of the little-known Boreal Chickadee (Poecile hudsonica), in a 66-km2 boreal forest harvested for timber near Québec City, Québec. From January to March 2004 and 2005, we followed flocks on snowshoes and recorded their trajectory in real time using a handheld global positioning system (GPS) receiver. Boreal Chickadee flocks showed no response to forest edges when using mature forest stands. However, flocks mostly used edges of regenerating forest habitat (4–7 m high). Inside regenerating forest, flocks were significantly closer to both open edges (41 ± 6 m) and mature forest edges (11 ± 2 m) than would be expected from a lack of response to edges. Boreal Chickadee flocks did not avoid exposed edges of mature forest on the coldest or windiest days. On colder days, they were found disproportionately more often along edges between mature and regenerating stands, but generally avoided exposed edges of regenerating stands. Increasing edge densities resulting from clearcutting in boreal forest did not have a negative effect on use of remaining mature-forest patches, even under inclement weather. However, in regenerating stands resulting from timber harvest, Boreal Chickadee movements may be restricted during harsh weather.
Réponse de Poecile hudsonica face aux bordures forestières en hiver: quelle est l'importance des conditions météorologiques?
