This is Scientific American — 60-Second Science. I'm Julia Rosen.
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Great frigate birds are extraordinary creatures. They're seabirds with six-foot wingspans, yet they weigh only about three pounds. Their preferred food: flying fish—which they pluck out of the air above the water's surface. Frigate birds' feathers aren't waterproof, so landing on the water to fish is a no-go.
Now, scientists have discovered that great frigate birds do something else amazing: they can fly for up to two months at a time without landing.
Researchers already knew that these birds took extended trips over the Indian and Pacific Oceans to feed. But in a new study, scientists used tracking devices to follow the movement and vital signs of birds from the island of Europa, near Madagascar. They discovered that the birds have a highly specialized strategy for staying aloft.
"When they are traveling, most of the time, they flap very infrequently their wings."
Henri Weimerskirch, an ecologist at the National Center for Scientific Research in France.
"In fact, what they are doing, they are doing sort of a roller coaster flight where they take altitude. Even they can climb up to 3,000 or 4,000 meters, and when they climb, they do not flap their wings at all."
Weimerskirch and his colleagues found that the birds climb currents of rising air associated with cumulus clouds, circling upwards the way hawks and vultures do over land. Then they glide back down again, hardly flapping. By using atmospheric conditions to their advantage, the birds covered an average of 420 kilometers a day almost effortlessly. The study is in the journal Science.
The researchers also discovered that the birds endure some harrowing conditions on their voyage, including some thrills and chills.
"When you enter into the clouds, there's a lot of turbulence. After, when you see from the recording on the logger of the bird, when they are at 4,000 meters, the temperatures are negative. It's a tropical bird. It's a bird that has no specific down like geese that are operating in the Arctic. So they are encountering sort of a polar temperature, but it's a typical tropical bird."
Of course, the birds have to eat during their journey. The researchers found that diving down to the sea surface to snatch a meal consumed most of the birds' energy, even though it only occupied about 10 percent of their time.
"When they are climbing, they have a period where there is no movement at all during several minutes. And so, during this time is probably the time when they are sleeping."
That's right—like many others who make long-distance flights, great frigate birds catch a little shut-eye along the way.
Thanks for listening for Scientific American — 60-Second Science Science. I'm Julia Rosen.
大军舰鸟是一种特别的生物 。它们属于海鸟，拥有长达6英尺的翼展，但重量只有3磅 。大军舰鸟偏爱的食物是可以在海面上捕获的飞鱼 。军舰鸟的羽毛并不防水，所以让它们降落在水面上捕鱼是不可能的 。
研究人员已经知道这些鸟会在飞过印度洋和太平洋的长途跋涉中觅食 。在一项新研究中，科学家使用追踪设备追踪马达加斯加附近欧罗巴岛上的军舰鸟的活动和生命体征 。他们发现，军舰鸟的高空飞行拥有高度专业化的策略 。
“事实上，它们所做的就是在它们所飞行的高度像过山车一样飞行 。它们甚至可以爬升到 3000或 4000米的高度，而它们在爬升时根本不拍打翅膀 。”
维莫斯克奇和他的同事发现，这些军舰鸟借助积云形成的上升气流盘旋爬升，就像老鹰与秃鹫一样 。然后它们会向下滑行，几乎不需要拍打翅膀 。利用对它们有利的大气条件，军舰鸟平均每天可以毫不费力地飞行420公里，这项研究结果发表在《科学》杂志上 。
“进入云层以后会遇到很多乱流 。查看军舰鸟追踪器上的记录时你会发现，它们在4000米的高度飞行时，温度已经在零度以下 。军舰鸟是一种热带鸟，就像在北极生活的鹅一样，军舰鸟也没有确切的活动时间，因此它们会遇到极低的温度，但军舰鸟是典型的热带鸟 。”
当然，军舰鸟肯定要在途中觅食 。研究人员发现，军舰鸟会潜到海面上捕食，这消耗了其大部分能量，即使这只占它们旅途时间的10% 。
“在爬升时，军舰鸟有几分钟的时间处于完全不活动状态 。这表明这段时间可能是它们的睡眠时间 。”
谢谢大家收听科学美国人——60秒科学 。我是我是朱丽亚·罗森 。
1. in fact 事实上，其实；
例句：She is by no means poor: in fact, she's quite rich.
2. be associated with (与…）相关的；相联系的；
例句：In children's minds, summers are associated with picnics.
3. to one's advantage （尤指转变不利情况使之）对…有利；
例句：It will be to his advantage if he studies hard.
4. even though 即使；尽管；纵然；
例句：I like her even though she can be annoying.