When Europeans first arrived in New Zealand the yellowhead was still abundant, but forest clearances, predation by introduced mammals and competition with introduced vespulid wasps (Vespula spp.) and birds all had a devastating effect on the species’ survival (3) (6). As a result, this bird has disappeared from 75 percent of its former range (4). As with much of New Zealand’s endangered fauna, habitat destruction has been a major cause of decline, with many forests still being cleared or modified by selective logging. Predation also poses a serious threat, with yellowheads suffering periodic population crashes when stoat (Mustela erminea) numbers erupt (4). These eruptions follow seasons of heavy beach seeding that occur every four to six years, which allow species up the food chain to multiply, with populations of insects, then mice, and then stoats, proliferating (4) (6). Stoats prey upon eggs, chicks and incubating adult females that are unable to escape from the nest hole, resulting in huge losses and a dramatically biased sex ratio (4) (6). Black rats (Rattus rattus) brought over on ships are also excellent climbers, and prey upon eggs, chicks and incubating females (3) (4). It is also thought that stoat control initiatives in certain areas may have reduced predation on the increasing rat population (3) (6). Competition for insects and honeydew from introduced vespulid wasps has contributed to the bird’s disappearance from beech honeydew forests in the northern South Island, and introduced finches are thought to also be competing for food and contributing to the species’ decline (6).