【BBC南太平洋】无尽汪洋 09
全文听写（以音频为准），英式拼写Hints:
Essex
frigate bird
http://t1.g.hjfile.cn/listen/201303/201303160627396928522.mp3The survivors of the Essex were at the mercy of sharks. As one sailor wrote, "Our utmost efforts, which were at first directed to kill him for prey, became, in the end, self-defence." Now, more than ever, they needed the salvation of land. Seabirds would have been a ray of hope. While tropic birds can survive at sea for months on end, others, like frigate birds, return to roost every night, so are a sure sign of nearby land. Guided by the sun, stars and the Earth's magnetic field, seabirds navigate over thousands of miles of featureless ocean. They must all return to land to breed, often on little more than dots of sand, which makes their navigational skills even more impressive.
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