Effects of forest roads on habitat quality for ovenbirds in a forested landscape

Numerous studies have reported lower densities of breeding Ovenbirds (Seiur us aurocapillus) adjacent to forest edges. However, none of these studies h as considered habitat use and reproductive success to address mechanisms un derlying the observed pattern, and most were conducted in fragmented landsc apes and ignored juxtapositions of forest with narrow openings such as road s. We studied the influence of forest roads on Ovenbird density in an exten sively forested region of Vermont, evaluating habitat use and reproductive success relative to mechanisms proposed to explain the density-edge relatio nship. Territory densities on seven study plots were 40% lower within edge areas (0 to 150 m from unpaved roads) than within interior areas (150 to 30 0 m from roads). We simulated the distribution of Ovenbird territories and concluded that passive displacement, where birds perceive habitat interface s as boundaries and limit their territories entirely to forest habitat, did not account for the observed density-edge pattern. Territory size was inve rsely related to distance from roads, providing an alternative explanation for reduced densities near edges and suggesting that habitat quality was hi gher away from roads. Pairing success was lower within edge areas than with in interior zones, but the difference was not statistically significant. Th e proportion of males that produced fledglings did not differ between edge and interior areas. We conclude that habitat quality for Ovenbirds may be l ower within 150 m of unpaved roads in extensive forested landscapes, affect ing territory density and possibly reproductive success.