Optimizing avian translocation success: A systematic review of the effect of release age on survival, dispersal, and productivity

Abstract

Abstract The success of avian translocations depends on many factors. Release age is often cited as an influential factor that warrants further study, yet no general guidelines exist to improve the outcome of translocations. We conducted a systematic review of literature on captive‐reared or wild‐caught birds that incorporated >1 age class in their analyses of post‐release survival, dispersal, or reproduction. Fifty‐two studies met our search criteria, and 39 were retained for an evaluation of post‐release survival. For studies reporting at least one trend, more reported higher post‐release survival when birds were translocated at younger ages (68%) than at older ages (32%). This pattern was most pronounced for wild‐caught birds and for captive‐reared birds released within their first year of life. Captive‐reared birds of prey were an exception, with birds released at older ages often having higher survival than birds released at younger ages. We review the authors' hypotheses for why birds released at younger ages are more likely to settle, survive, and breed. More research is needed on the potential effects of release age on dispersal and reproduction. We recommend that future studies incorporate age of release as a covariate and control for the effect of season of release in experiments.

Keywords

• age effects
• age of release
• captive breeding
• dispersal
• productivity
• reintroduction