Homing pigeons seem to have a compass built right into their heads.  They can be taken hundreds of miles from their homes.  When they are let go to fly again, they find their way home.

Scientists don’t know exactly how the pigeon’s “compass” works, but they have found tiny pieces of a special kind of iron, called magnetite, in homing pigeons’ heads.

These little pieces are natural magnets, and could enable the pigeon to sense direction from the Earth’s magnetic field.  Homing pigeons can also tell direction accurately from the sun’s position. –Dick Rogers