Scientists have several hypotheses to explain the homing flight of pigeons, and both are still debated. One hypothesis involves an “odor map,” in which young pigeons learn how to return to their original point of departure by smelling different odors that reach their home in winds from varying directions. They would, for example, learn that a certain odor is carried on winds blowing from the east. If a pigeon were transported eastward, the odor would tell it to fly westward to return home. Another hypothesis proposes that a bird may be able to extract its home’s latitude and longitude from the Earth’s magnetic field. Still another suggestion is that the birds are able to fly home by using learned landmarks. It may be proven in the future that none of these theories explains the pigeon’s navigational abilities—that some combination of the theories is the actual mechanism.
People often think of migration in terms of bird behavior, but sea creatures and land animals migrate, too. For example, the wildebeest of East Africa travel each year between the Masai Mara in Kenya and the Serengeti in Tanzania in what is called the Great Migration.