Area-sensitive forest birds move extensively among forest patches

摘要

Habitat fragmentation is thought to create a barrier to individual movements particularly for area-sensitive species which, by definition, prefer to breed in large tracts of forest. For two breeding seasons, we radio-tracked an area-sensitive species, the scarlet tanager Piranga olivacea, in a fragmented landscape in northeastern PA. We found that scarlet tanagers made extensive and frequent movements among fragments. Paired males were less likely to leave their capture fragment, and traveled shorter distances. Unpaired males in fragments had two distinct tactics we labeled: "Sedentary" and "Mobile". Sedentary males stayed at one fragment and sang at high rates, while mobile males spent 58% of the total time tracked off their capture fragment and traveled over a kilometer away from the capture site over open fields and through forests. Mobile males were not floaters per se because they were territorial (i.e., singing) in multiple sites. Habitat structure of a fragment did not correlate with the percent time a male spent of the capture fragment. Males in fragments experienced lower pairing success and were more likely to be first time breeders compared to males in continuous forest. Our results suggest that movements by scarlet tanagers in fragmented landscapes are not restricted during the breeding season, and that these movements are related directly to pairing status and indirectly to population density