Holocene extinction may have put some pressure on other birds but at the time of early European contact (18th Century) and colonisation (19th Century) the bird life was prolific. With them, the Europeans brought ship rats, possums, cats and mustelids which decimated native bird life, some of which had adapted flightlessness and ground nesting habits and others had no defensive behavior as a result of having no extant endemic mammalian predators. The kakapo, the world's biggest parrot, which is flightless, now only exists in managed breeding sanctuaries. New Zealand's national emblem, the kiwi, is on the endangered bird list. There has been
Kakapo non-dispersive sex when food is plentiful. A female kakapo will likely be able to produce eggs even when there are few resources, while a male kakapo will be more capable of perpetuating the species when there are plenty, by mating with several females. This supports the Trivers–Willard hypothesis. The relationship between clutch sex ratio and maternal diet has conservation implications, because a captive population maintained on a high quality diet will produce fewer females and therefore fewer individuals valuable to the recovery of the species. The beak of the kakapo is adapted for grinding food finely. For this reason, the