That really is amazing! I always thought they used some type of terrain mapping and they would follow certain points along the same route to go back and forth.
Homing pigeons can be dropped off hundreds of miles from their home and released. They find their way back to their roost. Their brains have a built in GPS system not fully understood, The most popular theory is a two dimensional system. One part being small iron deposits in the inner ear which acts as a compass. The second part is a crude form of terrain memorization. The compass gets them close to where they want to be, then their memory kicks in for the final pinpoint location.
