Island releases of saddlebacks Philesturnus carunculatus in New Zealand

The success of 45 releases of saddlebacks Philesturnus carunculatus between islands in New Zealand is compared. Forty-three releases were 'immediate' (birds released immediately on arrival at site), and two were 'delayed' (birds released after 12 days' conditioning in an aviary on site). Most releases with a balanced sex ratio on predator-free islands were successful. Others failed because (1) predators were still present, or arrived after release, or (2) too few birds were released. The success of releases may have been enhanced by the birds' limited dispersal, small territories, flocking behaviour, high reproductive rate and broad habitat requirements. Before one release, prior conditioning of the birds in an aviary on site did not improve their subsequent survival. Immediate releases should be used for wild-caught birds, and the captive period minimised. Conditioning may be appropriate for captive-reared birds to adjust to the wild. (C) 1996 Elsevier Science Ltd