白日渐短,树叶发黄、纷纷落下,天气转冷,冬天近了。人类居家有暖气,出门有棉衣,面对寒冬,动物们怎么办?迁徙是一个办法。许多动物,尤其是鸟类,一旦嗅到冬天的气息,就开始了一年一次、由北往南的漫漫旅程。这个过程充满危险,一些动物选择集体出行。比如天鹅,总是V型排开、热闹上路。北极燕鸥 Daydreams, yellow leaves, have fallen, the weather turns cold, winter is near. Human home heating, go out with a cotton coat, in the face of winter, animals how to do? Migration is a way. Many animals, especially birds, start their once-a-year long journey from north to south once they smell the winter's breath. This process is dangerous and some animals choose to travel collectively. Such as swans, V-always open, lively on the road. Arctic Tern