Predicting release success of captive-reared loggerhead shrikes (Lanius ludovicianus) using pre-release behavior

Abstract

We assessed whether behavioral markers could be used to evaluate pair compatibility and predict pair bond success of captive-reared San Clemente loggerhead shrikes (Lanius ludovicianus mearnsi) released into the wild. Potential breeding pairs of shrikes were introduced at the Zoological Society of San Diego's captive-breeding facility and then moved to release cages located in suitable but unoccupied habitat. Courting pairs were affected negatively by the disturbance of translocation to a new location and generally needed a few days to reinitiate pair bonding in the release enclosures. We separated and returned pairs to captivity when intra-pair aggression or cessation of all courtship behavior occurred; all other pairs were released into the wild. The rate of nest approaches was the best marker to predict a successful release into the wild (i.e., pairs that remained near the release site and attempted to breed). Additionally, all experienced breeding pairs (i.e., pairs with males and females with prior captive breeding experience) exhibiting nesting behavior were successful, although previous experience alone does not ensure post-release breeding. Results from this study indicate the importance of assessing behaviors of individuals paired for population augmentation. In using behavioral cues, identifying pairs with a low probability of success is possible, and replacing these pairs with individuals that have a higher likelihood of post-release success can occur. This strategy will be important to efficiently restore imperiled populations of endangered species while working within temporal and financial constraints. Zoo Biol 0:1–12, 2005. © 2005 Wiley-Liss, Inc.