冬去春来,燕子又开始北迁。虽然一年中要搬两次家,但它们从不会走错家门。一种身长仅350毫米的极燕鸥在北极营巢却在南极过冬。每年来回飞行4万多公里,从不迷路。这些候鸟识别方向的能力让人惊叹,也让人疑惑。在漫漫旅途中,它们是怎样保持飞行路线准确无误的呢?为了研究兵器导航仪,军事专家决定解开候鸟的导航之谜。专家设想,鸟类可能是按照太阳来确定方向的, Winter to spring, the swallow began to move north. Although moving twice a year in a year, they never go wrong. A 350-meter-long polar tern nesting in the Arctic and winter in Antarctica. Flying back and forth more than 40,000 kilometers a year, never get lost. The ability of these migratory birds to identify the direction of amazing, but also puzzling. In the long journey, how do they keep the flight route accurate? In order to study weapons navigators, military experts decided to solve the mystery of migratory birds navigation. Experts imagine that birds may be in accordance with the sun to determine the direction,