Some species of Arctic birds are threatened by recent sharp increases in the population of snow geese, 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。
2
Pythons breed rapidly, and the Burmese population is estimated to be in the thousands.
蟒蛇繁殖得很迅速，据估计缅甸蟒的数量将有数千条。
3
The future of slender-billed vultures in India may lie with the first of their kind to breed in captivity following a 97% crash in the species population since the 1990s - or it may not.