ABSTRACT

Despite efforts to recover the California Condor (Gymnogyps californianus) in the past 30 yr, the species is still Critically Endangered due in part to dependence on field management and captive breeding. Captive breeding focuses not only on the quantity of young produced every year, but also on the quality of these birds, to ensure their future success in the wild. In this study, The Peregrine Fund pioneered the use of unpaired adult condors as foster parents to increase the number of young being raised by conspecifics, and therefore likely increase their chances of success in the wild. A total of 17 young have been raised to fledging by unpaired adults with previous rearing experience at The Peregrine Fund's World Center for Birds of Prey from 2012 to 2019. Three unpaired males successfully raised eight young. An unpaired female raised young in 2018 and 2019 after her infertile eggs were switched with hatching eggs. We also separated a pair of condors and had each attempt to raise young on their own, for a total of seven young raised. The adult that remained in the original chamber always raised young successfully. The adult that was separated, however, often rejected the dummy egg that was offered in the new chamber. The use of unpaired adults as foster parents provides the recovery effort with additional benefits, such as having experienced breeders raising young, having “backup” parents, keeping unpaired adults occupied with breeding tasks, and preventing them from being housed as surplus animals.

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