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

41. 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
42. 0nce their eggs have hatched,
    一旦小鸟破蛋而出
43. they will be forced repeatedly to make the 600-mile round trip to gather food in the ocean.
    雪海燕将为觅食而不断往返海陆600英里
44. 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
45. 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
46. The south polar skua is a formidable opportunist.
    南极贼鸥是可怕的机会主义者
47. 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, 它们早就等着下手

来自《行星地球 第一季 第六集 Planet Earth S01E06 冰雪世界》第 44 行