Page 90 - The Miracle of Migration in Animals
P. 90

THE MIRACLE OF MIGRATION IN ANIMALS







































                                                        Left: The structure of the
                                                        magnetic field resembles
                                                        that of a coil. Its effect is
                                                        strongest at the poles
                                                        and weakens towards the
                                                        equator. Some birds have
                                                        been found to sense this
                                                        field, whose existence
                                                        people have discovered
                                                        only recently. But birds
                                                        have perceived this effect
                                                        for millions of years and
                                                        can easily determine
                                                        which way to go when
                                                        migrating.







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