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The snow petrels have arrived and are courting.
雪海燕来了，在这里求偶。
Antarctic petrels now join the most southerly bird colony on Earth.
南极雪海燕的领地在地球的最南方
The birds have flown inland for over 300 miles to reach this breeding site.
它们往内陆飞行300英里才来到这里繁衍
Once their eggs have hatched, they will be forced repeatedly to make the 600-mile round trip to gather food in the ocean.
一旦小鸟破蛋而出，雪海燕将为觅食而不断往返海陆600英里。
First, though, valuable nesting places must be defended from property thieves.
不过先得保护好来之不易的筑巢地，免得被其他鸟类占据。
After laying their eggs, the petrels take time out to clean their plumage.
产蛋后雪海燕会在抽出时间在雪地里整理羽毛
The south polar skua is a formidable opportunist.
南极贼鸥是可怕的机会主义者
But the skuas have not chanced upon the petrels, they've been waiting for them.
但是贼鸥碰到海燕并非机遇使然，它们早就在等着下手。
These birds do not need to go to the ocean for their food.
贼鸥不需要到海洋里捕食
The skuas can survive further south than any other predator
与其他猛禽相比，贼鸥的厉害在于它能在地球的最南端生存，
by exploiting the petrels' desperate need for bare rock.
它们知道利用海燕必定寻找裸岩筑巢的弱点。
