Humans like to pride themselves on their superior intelligence but when it comes to native intelligence they can't hold a candle to the lowly homing pigeon.
According to a report in the Economist, Jon Hagstrum, of the United States Geological Survey, has discovered yet another way that homing pigeons pull off their spectacular feats of navigation.
The story goes back to bird biologist, Bill Keeton, who experimented with these birds in an area of New York from Jersey Hill to Ithaca, known as the Birdmuda triangle. The strange thing was the birds kept getting lost. But on one day, Aug. 13, 1969 the pigeons mysteriously came right home. What was going on here?
Keeton knew that pigeons navigate by the sun and by the Earth’s magnetic field. But both of these are as available in upstate New York as anywhere else, so a third factor must be involved. Tackling the puzzle later, Dr Hagstrum set out to discover what it was.
He had a theory. Pigeons are now known to be able to hear very-low-frequency sound waves, called infrasound, such as are generated by ocean waves. This was information unavailable to Keeton, but Dr Hagstrum suspected it might be the missing part of the puzzle because infrasound can travel thousands of kilometres from its source.
An animal that can hear it might thus have a mental infrasound map that it could use as an aid to navigation. But why did the birds usually lose their way? Dr Hagstrum hypothesized that something about the location of Jersey Hill was casting a sonic shadow such that local pigeons could not hear their destination.
But why wasn't this shadow constant? Hagstrum examined Keeton's old reports and cross-referenced them with data on weather conditions on the days the experiments were done. He then reconstructed the atmospheric conditions on each of those days and used a computer program to calculate how infrasound would have travelled from the pigeons’ home loft to Jersey Hill.
He found that on every one of the days Keeton conducted an experiment, infrasonic waves from the direction of Ithaca would have been deflected away from Jersey Hill—except on August 13th 1969. On that day conditions were unusual and the infrasound was guided directly there. Able to hear the call of home, the birds returned safely.
Hagstrum also found that pigeons raised in a different area had no problem navigating the Birdmuda triangle. Evidence that they had not formed a navigational map in their brain based on the infrasound waves in that area as had the locally-raised pigeons.
Dr. Hagstrum had put the last piece of the homing-pigeon jigsaw puzzle in place. He concluded that pigeons form a far richer picture of the world than people do through three GPS navigational senses unavailable to humans: to the sun, to the Earth's magnetic waves and to infrasound waves.
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