The Diet of the North Island Kaka (nestor Meridionalis Septentrionalis) on Kapiti Island

New Zealand Journal of Ecology (1997) 21(2): 141-152 ©New Zealand Ecological Society spp.), and rats (Rattus spp.), may also be contributing to the decline of kaka by reducing the birds’ productivity (Beggs and Wilson, 1991). A significant competitive interaction with possums is suggested by the fact that kaka remain common in the South Island only where possum densities are relatively low (O’Donnell and Dilks, 1986). Supplementary feeding has not increased the low nesting frequency of a South Island kaka (N. m. meridionalis) population (Wilson et al., in press). This suggests that low productivity was not a consequence of competition for food with introduced species. Breeding in this population appears to depend on the availability of red beech (N. fusca) seed, a periodically superabundant food which is not limited by introduced species (Wilson et al., in press). However, as kaka have a diverse diet (O’Donnell and Dilks, 1994) and occur in a wide range of forest types (Oliver, 1974), competition with introduced species for food could be significant elsewhere. Supplementary feeding experiments can provide only limited evidence for or against competition. If supplementary feeding fails to increase productivity it is possible that insufficient food was provided to compensate for that consumed by competitors. Conversely, if supplementary feeding increases productivity, it does not follow that the population Introduction