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。

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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。

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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.

印度尖嘴秃鹰的未来也许取决于首次尝试的人工繁殖，自从1990年以来，它的数量已经减少了97%。

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They are the nurseries of the ocean, where many species of fish and shrimp breed and serve as a buffer against coastal erosion in a region where much of the population livesin low-lying areas.

VOA: standard.2010.03.29

The actual moment when a "daughter" species can (or will) no longer cross-breed with the population from which it sprang (the definition of speciation) is almost impossible to pinpoint, let alone to witness.

WSJ: Matt Ridley on the Possible Formation of a Species | Mind & Matter

One early-warning system: inserting rodents with depressed immune systems (known as "nude sentinels, " because they happen to be a hairless breed) into the general population of rodents--canaries in the coal mine, if you will.

FORBES: 200 Best Under a Billion

If people in this population meet and breed at random, it turns out that you only need to go back an average of 20 generations before you find an individual who is a common ancestor of everyone in the population.

BBC: Family trees: Tracing the world's ancestor