One of the most mysterious things in nature is the ability of certain creatures to find their way home. Sometimes, from great distances birds are not the only ones who can do this. Bees, Eels, and Salmon are able to return to a particular place after doing journeys, too.Most migrations take place between breeding grounds and regions where animals feed. For some animals, such as the lemming, the move is a one-way trip. Scientists call the movement emigration, because these animals never return to their homes. For other animals, such as birds, the migration includes a return trip home. Birds move in periodic migrations, or at regular times during their lives, and often to the same place year after year.Many experiments have been made with birds in an attempt to find out what guides them on their way home. In one case, seven swallows were taken 400 miles from home. When they were set free, five of them returned to their nests. In another case, a certain kind of sea bird was taken from its nests on the Welsh coast to Venice by plane. When it was released, it made its way home to its nests, a distance of 930 miles if it flew in a straight line.Migrating birds offer an even more amazing example of this ability. There are swifts and house martins that migrate from England to South Africa every year. They not only return to England the next spring, but many of them come back to nests in the very same house they nested the year before. They fly the incredible distance of 6,000 miles, one way.Certain types of butterfly migrate, too, and find their way home over long distances. In the tropics one can sometimes see the great mass flights of butterflies all flying steadily in one direction. They may go a thousand miles and more and then return again in another season.Despite all the efforts that have been made to explain how these creatures find their way home, we still have no sure explanation. Since many of the birds fly over great bodies of water, we cannot explain it by saying they use landmarks to guide them. Just to say they have an “instinct” does not really explain the right conditions. But the signals and guideposts they use on their flights are still a mystery to man.
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