Black Vultures are a familiar sight in the southern and eastern United States as they aggregate in the evening at large communal roosts or gather beside highways to feed on road-killed animals. Almost exclusively carrion feeders, they spend much of the day in flight searching for carcasses. Unlike Turkey Vultures (Cathartes aura), Black Vultures lack a highly developed sense of smell and so cannot find carrion by scent alone. However, they exploit the superior food-finding skills of Turkey Vultures by following them to carcasses and then displacing them from the food. The sight of one vulture descending to a carcass draws others from over a large area and dozens may assemble at a single carcass.
Black Vultures do not build a nest. Instead they lay their (usually two) eggs on the bare ground in a cave, hollow tree, abandoned building, or other dark recess. Pairs will continue to use a nest site for many years as long as breeding is successful. Black Vultures are monogamous and maintain long-term pair bonds. The pair associate closely year round and may feed their young for as many as eight months after fledging. This prolonged dependence of the young on their parents may, in part, be responsible for the strong social bonds with kin that Black Vultures maintain throughout their lives.
The communal roost is an important focus of the social life of Black Vultures. It serves as a meeting place for adults and their young and as an assembly point for foraging groups. The communal roost also appears to function as an information center, a site where unsuccessful foragers can locate food by following roost mates to carcasses. Aggressive interactions between adults partially control roost membership, and these interactions may serve to limit recruitment of non-kin to recently discovered food sources.
Although the Black Vultures' habit of communal roosting and its complex social behavior have been the subject of recent studies (Rabenold Rabenold 1983 , Rabenold 1986 , Rabenold 1987a , Rabenold 1987b ; Buckley Buckley 1996 , Buckley 1997 ), overall the species is still understudied. Only one long-term study of its breeding biology has been carried out ( Rabenold and Decker 1990 , Decker et al. 1993 ) and more studies of long-term population dynamics and breeding success are needed, especially in areas where abandoned buildings are not the primary nest sites. Black Vulture home ranges and use of foraging habitat have been described quantitatively in southern Pennsylvania and northern Maryland ( Coleman and Fraser 1989c ), but similar information is unavailable for other portions of the range.