SPATIAL AND HABITAT RELATIONSHIPS OF RED-EYED AND BLUE-HEADED VIREOS IN THE SOUTHERN APPALACHIANS

Abstract

Red-eyed (Vireo olivaceus) and Blue-headed (V. solitarius) vireos have similar foraging ecologies, similar songs, and occupy similar forest habitats. Evidence suggests, however, that the typical pattern of habitat and foraging segregation in sympatric vireos may not be observed in the southern part of their range of sympatry. We tested the degree of ecological overlap in the southern Appalachians of Virginia by asking whether these species segregate via interspecific territoriality or habitat use. We quantified response to heterospecific song, territory overlap, and habitat characteristics during the breeding seasons of 1997 and 1998. Red-eyed and Blue-headed vireos responded at low frequencies (9% and 2%, respectively; years combined) to the songs of the other species. Not surprisingly, given the playback results, approximately 54% of territories examined for each species overlapped with a territory of the other species. Within territories, both vireos used structurally similar habitat. Microhabitat composition, however, differed between species. Blue-headed Vireos occurred in areas with greater abundance of white oaks (Quercus spp.), conifers, and snags, whereas Red-eyed Vireo habitat had qualitatively greater abundance of red oaks and red maples (Acer rubrum). Red-eyed and Blue-headed vireo habitat was discriminated further by the presence of striped maple (A. pensylvanicum) and black locust (Robinia pseudoacacia) in the canopy of Red-eyed Vireo habitat, whereas conifers and black birch (Betula lenta) were more common at sites where Blue-headed Vireos were observed. Shrub species composition did not differ significantly between vireo habitats. Red-eyed and Blue-headed vireos showed only subtle habitat segregation at our study site in the southern Appalachians, and we found little evidence of interspecific aggression.