Science. 1981 Jan 30;211(4481):499-501. doi: 10.1126/science.211.4481.499.
New Zealand, like many other islands, has suffered extinctions of native species and successful introductions of exotic species. It has been uncertain whether the introductions caused the extinctions or whether the extinctions permitted the introductions. On New Zealand's Hauraki Gulf islands, which are unusual in their near lack of introduced mammalian predators and complete lack of mammalian browsers, exotic bird species abundant in mainland New Zealand forest and reaching these islands are virtually absent from unmodified forest. Exotic bird species disappeared from Cuvier Island's forest after elimination of mammalian predators and browsers. Hence extinctions of native species were not due to competition from introduced species but to other factors (such as mammalian predators and habitat alteration). Only after decimation of native species and forest alteration by browsing mammals could exotic birds invade forest.
新西兰和许多其他岛屿一样，经历了本地物种的灭绝和外来物种的成功引入。引入物种是否导致了灭绝，或者灭绝是否允许了引入，这一直存在不确定性。在新西兰豪拉基湾的岛屿上，情况很不寻常，因为这些岛屿几乎没有引入的哺乳动物捕食者，也完全没有哺乳动物食草动物，而在这些岛屿上，在新西兰大陆森林中丰富的外来鸟类物种实际上从没有经过修改的森林中消失了。在消除了哺乳动物捕食者和食草动物后，库维耶尔岛的森林中的外来鸟类物种消失了。因此，本地物种的灭绝不是由于来自引入物种的竞争，而是由于其他因素（如哺乳动物捕食者和栖息地改变）。只有在本地物种被大量消灭，森林被食草哺乳动物改变之后，外来鸟类才能入侵森林。
