Implications of captive breeding for the reintroduction of the Saker falcon (Falco cherrug) in Bulgaria

Abstract

Abstract. The Saker falcon (Falco cherrug) is a globally endangered species recovered in 2018 in Bulgaria. The only known active pair currently breeding in the wild in the country is made up of captive-bred and released birds, part of the first reintroduction programme for the species in Bulgaria and globally. As part of the project, sourced Saker falcons of known European origin are bred ex situ, the juveniles are parent-reared and released in the wild by means of the hacking method. The aim of this study was to evaluate the success and effectiveness of the captive breeding and rearing methods. The objective of the study was to investigate, compare and assess the results from fertilization, hatching, survival and hacking of captive bred Saker falcons registered over a 10-year period (2011-2021) at the Wildlife Rehabilitation and Breeding Centre (WRBC) Green Balkans, with a more detailed comparison of the breeding activities carried out in 2020 and 2021 (as the reintroduction programme was restarted in 2020). The results show more than threefold increase in output of laid eggs with the employment of the double clutching method in 2020 and 2021, and an overall 65% release rate of the hatched in the WRBC Saker falcons, for the investigated period.