(1)________________________________________________.Every year, millions of creatures feel the need to migrate and most people have seen the arrival or departure of migrating flocks of birds.In England, for example, we always know when autumn is coming,because flocks of swallows sit on the telegraph wires.Migration is not only seen in birds but also in reptiles.For example, turtles, and frogs; insects, such as butterflies;and mammals, such as seals, whales and bats.Many of these creatures can find their way over long distances.And how they do it is a mystery and a wonder to everyone,especially for those of us who have difficulty even reading a map covering 100 miles.(2)__________________________________________. Firstly, it is suggested,they navigate by using stars and planets for guidance.Secondly, some people think that these migrating mammals find their way by following the pole of the earth's magnetic field.Thirdly, some people think that migrating birds,insects and animals follow a certain smell or scent.Fourthly, another group of people believe that animals migrate by recognizing the geographical features.Fifthly, some people think that animals migrate by following the changes in temperature.(3)_________________________________________.
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作者: susan.sui 时间: 2013-6-25 15:56
one of the greatest mistery of nature is they in state to migrate.
there're several suggestions about how they navigate.
and finally there're people who follow in suppose they migrate by following the sound.
