A 30-year investigation on birds around the globe, carried out by the International Council for Bird Protection, has found that "inability to compete with foreign species" is the reason accounting for 20 percent of all extinctions, a cause ranking higher than environmental pollution.
國際鳥類總會過去卅年多次全球性的鳥類調查都證實：一地原生鳥類絕種的原因中，「無法與外來種鳥類競爭」佔了百分之廿強，比環境污染的影響還高。