Movement and Survival of Captive-Bred Saker Falcons Falco cherrug Released by Wild Hacking: Implications for Reintroduction Management

Abstract

Knowledge of the behaviour and survival of translocated individuals is vital for successful management of conservation programmes aimed at restoring species to their former distribution range. We examined movements and survival of 10 captive-bred Saker Falcons Falco cherrug fitted with satellite-received transmitters, which were released by wild-hacking in Bulgaria in 2012–2014. Chicks were parent-reared in captivity and transferred to hack cages when 25–35 days old in groups of 3–4 nestlings, where they were fed without direct human contact. After leaving the hack cages at 43–51 days old, fledglings were retained in the vicinity by food provisioning at the hack cage. Birds tracked by satellite remained in the vicinity of the hack cage for an average of 28 days (range 5–49 days) and post-dispersal survival was positively associated with the length of time spent in the hack vicinity. We found no significant difference in tracking period, as a proxy of survival, for translocated and wild-fledged Saker Falcons in Europe. The cause of transmission cessation was known for five birds; three were electrocuted by power distribution lines, one died after becoming trapped in a building and another was caught by falcon trappers in North Africa. Captive-bred birds exhibited similar movement and settlement behaviour as their wild congeners: dispersing at varied headings, establishing post-dispersal temporary settlement areas and migrating to discrete wintering ranges. Birds surviving to at least their second year showed some degree of natal philopatry, establishing summer ranges 45–160 km from their hack sites. Provisioning at feeding stations around the hack in 2015 and 2016 improved retention in the hack area to an average of 38 and 43 days, and apparent survival during the first 40-days after fledging was 97.7 and 98.9% respectively. A pair of Saker Falcons that bred in Bulgaria in 2018 and 2019 was from a trial cohort hacked in 2015, indicating that translocation of captive-bred birds can potentially be used to restore the species to this part of its former breeding distribution range.