SEASONAL FOREST-PATCH USE BY BIRDS IN FRAGMENTED LANDSCAPES OF SOUTH-CENTRAL PENNSYLVANIA

Abstract

We surveyed birds during breeding, migratory, and wintering seasons in forest patches of two fragmented landscapes in the Valley and Ridge Province of south-central Pennsylvania during 1994–1996. Our objective was to examine presence of species in relation to forest-patch size (<2, 6–20, 40–150, and >1,500 ha) and extent of regional fragmentation. Several species, particularly long-distance migrants (e.g., Eastern Wood-pewee [Contopus virens], Red-eyed Vireo [Vireo olivaceus], Wood Thrush [Hylocichla mustelina], Worm-eating Warbler [Helmitheros vermivorum], and Scarlet Tanager [Piranga olivacea]), were more likely to occur in larger forest patches than in smaller patches during the breeding and spring-migratory seasons. Short-distance migrants (e.g., American Robin [Turdus migratorius], Gray Catbird [Dumetella carolinensis], and Eastern Towhee [Pipilo erythrophthalmus]), responded to fragmentation at a regional scale and were more commonly encountered in the more fragmented landscape, particularly during migratory periods. Species observed during fall migration were not influenced by patch size. The Pileated Woodpecker (Dryocopus pileatus) responded positively to patch size in all seasons, whereas the Song Sparrow (Melospiza melodia) was influenced negatively by patch size in three of four seasons. More research should be conducted at sites during winter and migration to corroborate these results and to examine the role patch size may have in long-term survivorship of migratory birds.