Carry-over effects of nestling physical condition predict first-year survival of a critically endangered migratory parrot

Abstract

Conservation breeding programs are an increasingly important tool to help supplement declining wild populations, but captive-bred animals generally do not survive well post-release. Early life in captivity has the potential to influence growth and development, with impacts carrying over to affect survival. Understanding carry-over effects of captivity and consequences on survival is critically important for conservation efforts globally but remains poorly understood. We examined the relationship between early-life environment, physical condition, and juvenile survival of wild and captive-bred critically endangered orange-bellied parrots (Neophema chrysogaster). Using nestling growth models, we calculated a body condition index for 1,039 wild and captive-bred orange-bellied parrots hatched over six breeding seasons. Nestling body condition varied with year, provenance, and brood position. Wild nestlings had consistently higher body condition than captive-bred nestlings, and first-hatched nestlings were typically heavier than later hatched siblings. We then investigated first-year survival for 298 wild-born and captive-bred released parrots in the wild. Overall, first-year survival was 27.5%, and individual body condition was more influential than provenance in predicting survival. Our findings could be used to aid the selection of individuals for release that have the best prospects of surviving in the wild. This study addresses important questions about the post-release fitness of captive-bred animals, and our metric of assessing physical condition provides a straightforward tool for other conservation breeding programs to adapt management techniques to improve survival outcomes.