这种鸟一边飞一边睡觉

军舰鸟能够在开阔的海面上空连续飞行好几天。它不能停落在水面上，因为它的羽毛并不防水，所以它索性就不降落。这自然引出一个问题：它到底什么时候睡觉？

A frigatebird can stay in the air over open ocean for days at a time. It cannot land on water, because its feathers are not waterproof, so it simply does not come down. That raises an obvious question. When does it sleep?

研究人员给军舰鸟安装了小型脑电记录仪，然后放飞它们，答案就这样揭晓了。这些鸟能连续飞行长达十天不停歇。它们确实会在空中睡觉，而且常常只有一半大脑在睡，另一半保持清醒，还睁着一只眼睛。当它们借着上升的暖气流盘旋而上时，负责观察转弯方向的那一半大脑往往就是保持清醒的那一半。

Researchers answered it by fitting small brain recorders to frigatebirds and letting them go. The birds flew for up to ten days without stopping. They did sleep in the air, and often only half of the brain slept at once, with the other half awake and one eye still open. When they were circling upward on warm rising air, the half watching the turn tended to be the half still awake.

真正令人惊讶的是睡眠时间的多少。在海上，这些鸟一整天只睡大约四十分钟，而且是以几秒钟为单位的短暂片段。回到陆地上后，同样的鸟却能睡上超过十二个小时。也就是说，它们能靠几乎不睡觉撑过一整个星期，然后回到陆地上把觉全部补回来。

The amount is the surprising part. Out at sea the birds slept about forty minutes in a whole day, in short bursts of a few seconds each. Back on land the same birds slept more than twelve hours. So they can run on almost no sleep for a week, and then they go home and pay it all back.