Landscape effects mediate breeding bird abundance in midwestern forests

We examine the influence of both local habitat and landscape variables on a vian species abundance at forested study sites situated within fragmented a nd contiguous landscapes. The study was conducted over a six year period (1 991-1996) at 10 study sites equally divided between the heavily forested Mi ssouri Ozarks and forest fragments in central Missouri. We found greater sp ecies richness and diversity in the fragments, but there was a higher perce ntage of Neotropical migrants in the Ozarks. We found significant differenc es in the mean number of birds detected between the central Missouri fragme nts and the unfragmented Ozarks for 15 (63%) of 24 focal species. We used s tepwise regression to determine which of 12 local vegetation variables and 4 landscape variables (forest cover, core area, edge density, and mean patc h size) accounted for the greatest amount of variation in abundance for 24 bird species. Seven species (29%) were most sensitive to local vegetation v ariables, while 16 species (67%) responded most strongly to one of four lan dscape variables. Landscape variables are significant predictors of abundan ce for many bird species; resource managers should consider multiple measur es of landscape sensitivity when making bird population management decision s.