Control of introduced mammalian predators improves kaka Nestor meridionalis breeding success: reversing the decline of a threatened New Zealand parrot

Abstract

The kaka ( Nestor meridionalis) is a threatened, endemic New Zealand parrot that is declining primarily because of predation by introduced mammals. Numbers of female kaka surviving to sexual maturity more than compensated for adult female mortality at three sites with predator control but not at three unmanaged sites. Nesting success at the sites with predator control was significantly greater (⩾80%) than at unmanaged sites (⩽38%) while predation on adult females was significantly less (5% c.f. 65%). Predation was the most common cause of nesting failure at all sites. Stoats ( Mustela erminea) appeared to be the main predator, although evidence of possum ( Trichosurus vulpecula) predation on eggs, nestlings and nesting females was also found. These results suggest that control of stoats and possums can potentially reverse the decline of the kaka on the main islands of New Zealand.