Fragments are not islands: patch vs landscape perspectives on songbird presence and abundance in a harvested boreal forest

The boreal mixed-wood forest of northern Alberta, Canada is characterized b y a mosaic of deciduous and coniferous forest patches. Recently, the decidu ous portion of the forest was allocated for industrial logging. Widespread habitat loss and fragmentation may negatively affect birds and other wildli fe. Most research on the effects of habitat loss on bird abundance has focu ssed on the forest as a patch or island in a matrix of non-habitat, but som e species of songbird may use both the forest patch and the matrix. We hypo thesized that some species of songbird might be able to compensate for a lo ss of deciduous forest by moving into other habitat types (termed "habitat compensation"). We report on a replicated field investigation in which we a ssessed the response of songbirds to commercial timber harvest by first exa mining their abundance within deciduous forest only, and then adding the cl earcuts and coniferous forest in the surrounding areas to the analysis for a broader, landscape view of the system. Bird communities in deciduous and coniferous habitats bad significant overlap in species composition; there w as less overlap between forest and clearcuts. The shift from patch-centred to landscape sampling altered our interpretation of over half of the most c ommon species responses to logging in at least one year, suggesting that ha bitat compensation may have been occurring. However, significant variation in responses of species was observed between the two study areas. Our past reliance on island biogeographic and other single habitat approaches may be inappropriate for this system, and we stress that a broad, landscape view is required to properly assess and interpret species' responses to habitat loss and fragmentation.