Landscape context and fragmentation effects on forest birds in southern Ontario

We examined the effects of patch size, local forest cover, and regional for est cover on the numbers and species composition of forest birds detected d uring fixed-radius point counts in 287 forest patches in four replicate stu dy areas in southern Ontario. Each study area consisted of two subareas dif fering in regional forest cover. The number of forest-interior species (as classified from the literature) detected per count, after controlling for f orest patch size, tended to be higher in subareas with greater regional for est cover, but this effect was much stronger, in some study areas than othe rs. In contrast, numbers of edge species and interior-edge generalists were higher in subareas with lower regional forest cover. Within study areas, t he number of forest-interior species increased and edge species decreased w ith both woodlot size and core area (amount of forest > 100 m from an edge) , but total species diversity at a point was relatively unaffected. Analyse s of individual species generally corroborated the patterns, except that so me so-called interior-edge generalists were more likely to be detected in l arge woodlots, while others were more likely in small woodlots. There was a tendency for the loss of forest-interior species with decreasing woodlot s ize to be greatest in subareas with low regional forest cover. In the conte xt of highly fragmented landscapes such as southern Ontario, where many for est-dependent species have become rare, forest conservation should focus on protecting or restoring larger forest tracts in areas with substantial rem aining regional forest cover.