Postrelease survival of captive-bred Egyptian Vultures is similar to that of wild-hatched Egyptian Vultures and is not affected by release age or season

Abstract Reintroducing species to their historic range or reinforcing extant but endangered populations with individuals from elsewhere are popular conservation efforts to maintain long-term viable populations of animals. These efforts, known as conservation translocations, require proper monitoring of the fate of the animals that are released to assess their success. Nevertheless, effective monitoring is often missing in conservation translocations. Here, we assessed the efficiency of different monitoring methods and estimated survival of captive-bred Egyptian Vultures (Neophron percnopterus) that were released to the wild during the first 15 years of a reintroduction project in Israel. First, we inspected data obtained from different monitoring methods and compared observations of color rings and wing tags to location data from GPS transmitters. Then, we used GPS data to estimate apparent survival of vultures that were released to the wild at different ages and different seasons. Finally, we compared the apparent survival of captive-bred and wild-hatched Egyptian Vultures. We show that only a relatively small portion of the birds were visually observed through color rings and wing tags, compared to those for which data were obtained from GPS transmitters. Using data obtained via GPS transmitters we were able to show that release age and season did not alter apparent survival. In addition, we found no differences in apparent survival between captive-bred and wild-hatched Egyptian Vultures during their first migration or during their first two years postrelease or postfledging. Our results show the importance of continuous and effective monitoring and confirm the efficacy of captive-breeding and release of Egyptian Vultures as a conservation tool. We recommend the continuation of monitoring using GPS transmitters, alongside increased observation-based monitoring efforts.