Food Habits of Black and Turkey Vultures in Pennsylvania and Maryland

Abstract

In 1983 and 1984, we studied black (Coragyps atratus) and turkey (Cathartes aura) vulture foraging behavior in Pennsylvania and Maryland by observing 21 radio-tagged vultures and collecting 134 regurgitated pellets. Radio-tagged vultures consumed 21 different kinds of carrion. Domestic animals were consumed more often (62%) than wild ones (38%). Black vultures fed more on large carrion (>20 kg) than did turkey vultures. Remains in pellets indicated greater use of wild sources of carrion than did observation of radio-tagged birds, possibly because large, domestic carrion was more digestible. Sixty-five percent of feeding was initiated from 3 to 7 hours after sunrise. Black vultures fed earlier, foraged in larger groups, fed longer at fewer locations, and fed closer to the main communal roost than did turkey vultures. Vultures use of domestic carrion makes the establishment of feeding stations a practical method of supplementary feeding. The 2 species may benefit unequally from feeding programs because of different foraging strategies. J. WILDL. MANAGE. 51(4):733-739 Although black and turkey vultures are present in many areas of North America, both species are declining in some regions (Brown 1976). These species have been little studied, and the causes of reported declines are unknown. Both species weigh approximately 2,000 g, and Prather et al. (1976) reported that captive turkey vultures consume approximately 140 g of food each day, yet little is known about food habits or feeding behavior of either species. The few existing reports about these species' food habits are either anecdotal (Pearson 1919) or are based primarily on regurgitated-pellet analysis (Thiel 1976, Paterson 1984, Prior 1986, Yahner et al. 1986). Although this method can provide information about some of the prey eaten, highly digestible items tend to be underestimated, and carrion with a large component of indigestible material is overestimated. Food availability may be an important factor in communal roost dynamics, shifts in vulture distribution, and competition between the species. To add to the understanding of vulture foraging dynamics we determined the species of animals that made up their food resource, the origin of these animals (domestic or wild), the distribution of carrion used (small and dispersed vs. large and clumped), and differences between the 2 species' food habits. We thank the Eastern Parks and Monument Assoc., the Natl. Park Serv., and Virginia Polytechnic Inst. and State Univ. for funding and logistic support of this research. Thanks to L. Haynes, H. Greenlee, T. D. Alderson, C. A. Pringle, M. R. Richmond, M. Tenney and J. Roberts for help with collection and analysis of the data.