How do birds know where to go when they migrate?
This question has fascinated scientists for centuries, and we are only beginning to know how some birds find their way during long migrations. Birds are born knowing that they must migrate, but knowing that is not the same as knowing how to get from a woodlot in Wisconsin to a jungle in Brazil or from a sea cliff in Alaska to a feeding ground in the Antarctic. We know that some birds are born with a “star map” coded into their brains that allows them to navigate by the position of the stars and the moon. Some birds use the earth’s magnetic field to find their way, and some use subsonic sound, the low-level noise created by ocean waves. Still others, like geese and swans, make their migrations in family groups, led always by an older bird that has made the flight before. There is still much to learn, however, about how birds make such long flights and find precisely the right spot.
