Bird Navigation

Experiments performed during recent years have strongly suggested that birds use the earth's magnetic field for navigation when they cannot see the sun or stars. The thought has been that when all else failed, the birds fell back to using the magnetic field to steer them. Now, a new experiment suggests that homing pigeons use the magnetic field as a preferred rather than a secondary guide.

Reporting in the October 16, 1981 issue of Science, German scientists described what happened when they released several different groups of pigeons on sunny days early in the morning. In one group were normally raised pigeons that had been exposed to the sun during all times of the day. When released, this group headed for home. The pigeons in a second group had never in their lives seen the sun before noon. They too flew for home without trouble, obviously using something other than the sun for guidance.

A third group of pigeons which also had not ever seen the forenoon sun but which had strong magnets glued to their backs were disoriented and flew off in random directions. They had neither the sun nor the earth's magnetic field to guide them, since the magnets they carried were strong enough to prevent the birds' sensing of the earth's magnetic field. Had these birds preferred to use the sun rather than the magnetic field, they should have flown in the direction opposite to home.

Thus this set of experiments, and other recent experiments of similar nature, seem to be pointing toward the idea that birds may be using the earth's magnetic field as a primary guidance source. They also use the sun and the stars, but these probably are secondary guides.