Corticosterone responses and post-release survival in translocated North Island Saddlebacks (Philesturnus rufusater) in New Zealand

The translocation of wild birds, commonly conducted as part of management of threatened and endangered populations, is a potentially stressful procedure that may have an impact on their subsequent survival. Corticosterone is the main avian stress hormone, and we examined the relationship between the corticosterone response to initial capture and handling, change in mass during a short period of captivity between capture and release, and subsequent survival after release during a translocation of North Island Saddlebacks (Philesturnus rufusater), an endemic New Zealand bird. In common with other birds, Saddlebacks had marked corticosterone responses to capture and handling. Saddlebacks confined in aviaries for 1-2 days between initial capture and release lost mass, but those confined for 3 days gained mass. The change in mass of birds after one night of confinement was not correlated with the initial corticosterone response. Survival after release to one year was high (70%) relative to four other monitored North Island Saddleback translocations (mean 53%, range 41-71%) but was not related to corticosterone response. The absence of a relationship between corticosterone response and survival may reflect benign conditions at the translocation site as suggested by this high rate of survival. The relationship between this acute corticosterone response and chronic stress and whether these physiological responses may potentially predict how individuals cope with these protocols warrants further investigation.