Releasing Captive-Reared Andean Condors to the Wild

Abstract

To develop techniques for future releases of captive-reared California condors (Gymnogyps californianus) to the wild, we used captive-reared Andean condors (Vultur gryphus) as surrogates. Hatched at facilities in the United States, 11 young Andean condors were transported to an isolated study site on the coast of northern Peru and released under experimental conditions. Six of these condors were raised by their parents then held with other juveniles in large aviaries before being shipped to Peru. They were between 1 and 3 years old when released. The other 5 condors were hand reared with the aid of puppets that closely resembled adult condors. They were released at the age when natural fledging occurred. Over periods of 170-260 days we taught these released birds how to forage by placing carcasses at progressively greater distances from the release site until the birds' foraging area was large enough that they encountered natural carcasses more frequently than those we offered. At this point they rapidly became independent of our care. The 6 birds released at an older age integrated with the wild population more rapidly than did the 5 birds released at fledging age; however, we had better control over the behavior and movements of the fledgingage birds. Seven of the 11 birds successfully reached independence and survived >18 months after their release. J. WILDL. MANAGE. 51(3):541-550 With only a small remnant population of California condors surviving in the wild (Snyder and Johnson 1985, Temple 1985), some conservationists believe that captive propagation and subsequent release of progeny to the wild is the most effective means of increasing the critically low numbers of this endangered species (Ricklefs 1978). Current management plans rely heavily on this concept, and a captive population is well on its way to being established (Meyer 1983; Temple 1983b, 1985). Furthermore, reproductive manipulations of captive California condors, such as multiple clutching (Cade 1978), could increase their normal fecundity several fold. This approach has worked with a close relative, the Andean condor, in which captive birds have produced up to 3 young annually rather than 1 every other year as is typical of wild birds (Bruning et al. 1981, Erickson and Carpenter 1983). Because large numbers of condors could conceivably be produced in captivity, there is a concomitant need to develop procedures for releasing, to the wild, condors that have been reared in captivity. Although procedures for releasing several other types of captive-reared birds to the wild have been successful (e.g., Bump 1951; Wayre 1975; Ellis 1978; Temple 1978, 1983a; Barclay and Cade 1983), condors have several traits that seem to make their release more difficult. These include: very slow rates of physical and behavioral development, long periods of parental dependency, special foraging behaviors that must be learned, and acquired social behaviors that are needed in interactions with other individuals. Our pr vious experiments with releasing captive-reared black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) helped us identify some basic procedures that apply to vult res and provided us with a general model for work with condors (Wallace and Temple 1983). In this paper we report on our efforts to devel p and test condor release procedures through xperimentation with Andean condors in orthern Peru between May 1980 and August 1984. We thank our principal field assistants, T. W. Torres, C. C. Christensen, J. F. Hoffman, L. M. Hecht, and P. K. Schoonmaker. Others who assisted us over the 3 years of the study are: C. S. Asa, S. L. Brantley, B. T. Clavenna, R. S. Clavenna, C. C. Gallaghar, S. A. DeStefano, C. Hays, D. C. Jenkins, C. J. Jenkins, E. Ortiz T., S. P. Palomino, G. del Solar, T. A. Luscombe, E. Santana C., C. A. Riebe, H. Snyder, J. C. Ogden, J. A. Carpenter, N. F. R. Snyder, D. H. Rusch, P. K. Ensley, and D. F. Bruning. This study was supported by the U.S. Fish and Wildl. Serv. Special thanks to the Metro Zoo of Miami, Fla., for contributing condor eggs to the project and to the N.Y. Zool. Soc. and Patuxent Wildl. Res. Cent. for handling the eggs and young condors in the United States. Permits to work at various