Some species of Arctic birds are threatened by recent sharp increases in the population of snowgeese, which breed in the Arctic and are displacing birds of less vigorous species.
某些种类的北极鸟受到近来雪雁数量急剧增加的威胁，这些雪雁在北极繁殖，并且正在取代生命力较弱的鸟类。
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Snowgeese travel thousands of miles to their winter homes.