Magnetic maps in pigeons.

The homing of racing pigeons is often slowed down on days of high sun-spot activity or variability in the earth's magnetic field. The orientation of Ring-billed Gull chicks as well as the vanishing bearings of homing pigeons also seem to change in response to variability in the earth's magnetic field. Furthermore, homing pigeons released under sunny skies at locations where the earth's magnetic field is distributed are disoriented, yet pigeons equipped with devices that change the magnetic field around their head home normally. Weighing all this evidence, it is hard to believe that pigeons use a magnetic map.