The role of introduced predators and competitors in the decline of Kaka (Nestor meridionalis) populations in New Zealand Original Research Article

We investigated the role of introduced predators and competitors in the population decline of kaka, Nestor meridionalis, a previously abundant forest parrot endemic to New Zealand. We provided supplementary food to test if a shortage of high energy food was limiting breeding in kaka. However, because most nesting attempts suffered from predation and we could not establish a non-treatment area, the role of competitors is still unclear. Kaka only bred in years when beech (Nothofagus) seeded. Over 11 years and 20 breeding attempts we recorded only four fledglings surviving to independence. Nine young kaka and four adult females were killed on the nest. We suggest that stoats were predominantly responsible for this predation. Kaka are relatively common on offshore islands without stoats, even in the presence of other predators and competitors, but are scarce on all islands containing stoats. We predict that stoat predation will cause kaka to become extinct on mainland New Zealand unless stoats and/or kaka are managed.