This species is undergoing a continuous decline, and in the last 45 years (three generations) has suffered a 10% population loss. Reasons for this marked decline include extensive habitat losses, due to forest clearing, pressures from hunting, predators and introduced competitors (4).
The predators include stoats, (Mustela erminea), which kill adults, and brush-tailed possums (Trichosurus vulpecula), which rob nests and eat kaka eggs. Stoats actually kill more females than males, as they are easier prey while incubating eggs. This may account for the highly skewed sex ratio on the mainland. Food competition on this island is also thought to be a problem for the kaka despite it having a mixed diet. The brush-tailed possum (Trichosurus vulpecula), black rat (Rattus rattus) and introduced wasps (Vespula spp) all compete with the kaka for various food, from invertebrates to honeydew (4).