Magnetic orientation in homing pigeons

Homing pigeons appear to use both a "map" and "compass" system to find their way home. Under sunny skies, the sun is used as a compass. But when the sun is obscured, pigeons appear to use the earth\´s magnetic field. The sensory basis of the pigeon\´s map is unknown but the disorientation of pigeons at magnetic anomalies under sunny conditions suggests that the map may be partly based on magnetic cues. Recently small deposits of the mineral magnetite have been found in two regions of the pigeon\´s head. It is conceivable that this material may somehow be involved in the pigeon\´s sensitivity to magnetic fields.