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 of the birds had died and the fifth died after about four years. In the next 12 years, regular expeditions found few signs of the kakapo, indicating that numbers were continuing to decline. Only one bird was captured in 1967; it died the following year. By the early 1970s, it was uncertain whether the kakapo was still an extant species. At the end of 1974, scientists located several more male kakapo and made the first scientific observations of kakapo booming. These observations led Don Merton to speculate for the first time that the kakapo had a lek breeding system. From