for National Geographic News
No wonder homing pigeons seldom get lost: They may get directions from their beaks. This intriguing idea is raised by a new study on the navigational abilities of birds published in tomorrow's issue of the science journal Nature.
The study raises the possibility that homing pigeons use a magnetic "map" inside their beaks for long-distance journeys.
Researchers say their study proves for the first time that homing pigeons can sense Earth's magnetic field.
The findings add to the debate over whether pigeons and other birds chart their flight paths by using a magnetic sense or by following scent clues in the atmosphere.
"The question of how [pigeons] might find their way home has fascinated laymen and academics for several decades," said Cordula Mora, a biologist at the University of North Carolina at Chapel Hill.
Descended from wild rock doves, homing pigeons can locate their lofts, or roosts, even when released several thousand miles away. Because of this ability, people have used the birds to carry messages since the days of ancient Egypt.
"We know that pigeons have a magnetic 'compass' and a sun compass. But there has been a long debate over the nature of the 'map' that pigeons use in conjunction with these compasses," said Mora, the lead author of the study. "The two main theories are that pigeons smell their way home using an olfactory map, or that they have a magnetic map."
Seeking to test the magnetic-map theory, Mora and her colleagues placed the birds in a wooden tunnel outfitted with feeding platforms at opposite ends and magnetic coils on the exterior.
The researchers then trained the pigeons to fly to one feeder if the magnetic field inside the tunnel was undisturbed and to the second feeder if the coils were switched on.
The researchers found that the birds' ability to select the correct feeder was significantly impaired if the birds had small magnets attached to their beaks. The scientists suggest this is because magnetite, an iron-rich crystal with magnetic properties, is found inside the homing pigeons' beaks.
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