Home range, habitat use, behavior, and morphology of the Gettysburg vultures

Abstract

I investigated several aspects of black vulture (<u>Coragyps atratus</u>) and turkey vulture (<u>Cathartes aura</u>) ecology in southcentral Pennsylvania and northern Maryland. Black and turkey vultures did not move randomly over the study area but remained within large (X̅ = 15,993 and 62,953 ha respectively) home ranges. Ninety five percent of radioed vulture activity was within 15 km of the location at which the birds were trapped. Although home range size was not different between species, turkey vultures had greater variation in home range size. Within home ranges, while perched or roosting, vultures preferred forests and undeveloped areas and avoided cropland and urban areas. Nesting vultures only used caves within forested diabase rock formations. While feeding, birds preferred pasture and cropland and avoided forest and urban areas. Farm carrion was an important food resource for both species. Black vultures fed more on carrion greater than 15 kg in size than did turkey vultures. In winter vultures fed sooner after sunrise than in summer. Black and turkey vultures began laying eggs in mid-March and mid-April respectively. Nestling growth rates were higher for turkey vultures than for black vultures. Productivity as calculated by the Mayfield method was 0.73 and 0.42 young per active nest for black and turkey vultures respectively. Planned vegetation and road changes on Gettysburg National Military Park could affect the populations. Residential development outside the Park has had and will continue to have detrimental impacts on nesting habitat.