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Homing Pigeons Concorde Causes Lost Pigeons?

By Discovery.com News

March 17, 2000 -- Although it helps humans move across the globe quickly, the Concorde may be responsible for making thousands of homing pigeons arrive home late.

As reported in this week's issue of New Scientist, California geophysicist Jon Hagstrum has found evidence that the supersonic shock waves caused by the jet may prevent pigeons from hearing a low-frequency sound that helps the birds find their way home.

Scientists have shown that the pigeons have an innate "compass" that enables them to navigate by using Earth's magnetic field and the sun's position. However, in order to reach their destination, the pigeons must also have a "map sense," or a mental chart linking their starting position with their destination.

"Nobody has been able to understand how they do that," Hagstrum told New Scientist.

Some researchers believe the map sense is based on infrasound -- extremely low-frequency sounds audible to birds, but not to humans. Waves exert pressure on the seabed, causing the land to shake, which in turn radiates infrasound into the air. According to Hagstrum, steep hillsides cause the sound waves to move horizontally, possibly creating beacons for birds to travel by.

Hagstrum became intrigued by the effects of supersonic planes when he learned that during pigeon races most of the birds are late or permanently lost. In 1997 alone, a third of the 60,000 British pigeons released in Nantes, France, did not return to England and the rest arrived late.

Hagstrum studied four pigeon races and found they all had one thing in common: The pigeons had to cross the path of the Concorde's infrasonic shock waves during their trip.

To test his theory, Hagstrum compared the birds predicted routes home and departure times of each of the races with Concorde data for the same time. In each race, the birds would have entered the cone-shaped shock wave, possibly temporarily or permanently deafening the pigeons to the infrasonic beacons.

Bird navigation expert Bob Beason of the State University of New York in Geneseo said Hagstrum's work is intriguing and follows current pigeon navigation theory. "The idea that pigeons might use infrasound for orientation has been around for a while," he told New Scientist.

Beason said Hagstrum has more work to do to prove that the Concorde is to blame for lost pigeons.

Copyright ) 2000 Discovery Communications Inc. http://www.discovery.com/news/briefs/20000317/animals_pigeons.html

-- (Dee360Degree@aol.com), March 19, 2000