How do birds know where to migrate?
Birds find their way using several tools: the Sun, the stars, Earth's magnetic field, landmarks such as coastlines and rivers, and possibly smell. Many also inherit a sense of direction.
Many birds use the Sun as a compass during the day, adjusting for its movement with their internal clock. Night-flying birds learn star patterns around the North Star when they are young. Experiments in planetariums showed that birds change direction when the artificial stars are moved.
Birds can also sense Earth's magnetic field. Scientists think special proteins in their eyes, called cryptochromes, may let them see magnetic lines, and iron-containing cells in their beaks or ears may help detect magnetic strength. As they get closer to their destinations, birds rely more on familiar landmarks.
Born knowing the way
Young cuckoos migrate from Europe to Africa alone, without ever having seen the route, guided by inherited instinct. Experiments with birds raised in captivity show they become restless and face the right direction at migration time, even without being taught.
Did You Know?
Homing pigeons can find their way home from hundreds of kilometers away, and scientists still debate exactly which senses they rely on most.