psittaciformes

To test the long-term efficacy of mammalian pest control, annual distance sampling estimates of the density of North Island kākā (Nestor meridionalis septentrionalis) within the southern Waipapa Ecological Area (WEA), Pureora Forest Park from 2008–2020 are compared to previously published estimates made at the same sites and time of year (October) between 2000–2007. Kākā density increased approximately four-fold from an average of c. 0.5 (95% CI 0.5–0.6) birds ha⁻¹ between 2000 and 2007 to c. 2.3 (95% CI 1.9–2.8) birds ha⁻¹ in 2020.

Intraspecific variation can have important knock-on effects on population dynamics and ecosystem processes. There are good indicators that intraspecific differences may exist in the foraging ecology of kea parrots (Nestor notabilis). Kea breed in two markedly different habitats (alpine and temperate rainforest), and have pronounced sexual size dimorphism of their upper bill, which may indicate niche partitioning between the sexes.

The diet of red-crowned parakeets (Cyanoramphus novaezelandiae novaezelandiae) and yellow-crowned parakeets (C. auriceps auriceps) was compared on Little Barrier Island, New Zealand between 1986 and 1987. Significant dietary differences were observed in these sympatric, congeneric species. Yellow-crowned parakeets ate significantly more invertebrates than red-crowned parakeets, which fed on a greater variety of plant foods.