Winter Use and Habitat Characteristics of Vulture Communal Roosts

Abstract

We examined winter use and characteristics of 16 communal roosts used by black (Coragyps atratus) and turkey (Cathartes aura) vultures during 1986 and 1987 in southern Pennsylvania, northern Maryland, and northeastern Virginia. Eight roosts were classified as primary and 8 as secondary based on numbers of vultures per roost and on frequency of use in both winters. Roosts had a greater density of conifers and larger trees (deciduous and coniferous) than random wooded sites and presumably provided vultures nocturnal perches with favorable microclimates, increased food availability, and enhanced soaring conditions. Roosts that contain large conifers (>56 cm dbh and >21 m tall) and are near (50-200 m) habitat features that contribute to air currents should be preserved for wintering vultures. J. WILDL. MANAGE. 54(1):77-83 Populations of black and turkey vultures in the Mid-Atlantic region have declined in recent decades (Brown 1976). A knowledge of both winter use and habitat characteristics associated with communal roosts is required to manage habitat for wintering populations of vultures. Previous studies of vulture roosts focused on roost dynamics (Sweeney and Fraser 1986, Taylor 1986), behavioral interactions and movements (Stewart 1978; Rabenold 1983, 1986; Coleman and Fraser 1989), and thermoregulation (Byman 1985, Clark and Ohmart 1985). With the exception of 1 communal vulture roost study in southcentral Pennsylvania (Wright et al. 1986), little is known about winter use and characteristics of roosts in the Mid-Atlantic region. Our objectives were to determine winter use of communal roosts by black and turkey vultures in southern Pennsylvania, northern Maryland, and northeastern Virginia and to describe habitat characteristics of communal roosts. J. D. Fraser, H. G. Hughes, and W. L. Myers reviewed the manuscript, and J. W. Grimm provided statistical advice. We thank J. S. Coleman and W. L. Myers for comments on the manuscript and J. F. Karish and H. J. Greenlee for cooperation with all aspects of the study. Funding was provided by the Max McGraw Wildlife Foundation, the Pennsylvania Cooperative Fish and Wildlife Research Unit, and the Jesse Rossiter Rapp Scholarship of the School of Forest Resources, The Pennsylvania State University. This is Journal Series Paper 7892 of the Agricultural Experiment Station, The Pennsylvania State University, University Park.