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The BBC's Sue Nelson reports
"Pigeon racing is a popular world wide sport"
 real 28k

David Glover, British Homing World
"I think this is a little dubious myself"
 real 28k

Thursday, 16 March, 2000, 13:53 GMT
Concorde sends pigeons off course
Concorde BBC
Concorde: May "deafen" the birds
Shock waves from Concorde may be to blame for the mysterious disappearance of thousands of homing pigeons, scientists believe.

The supersonic airliner could "deafen" the birds, preventing them from hearing the low-frequency sounds that may help them to find their way home, New Scientist magazine reports.

In June 1997, 60,000 English pigeons were released in France and around a third of them were never seen again. It has now been suggested the birds lost their way after crossing the path of low frequency shock waves generated by Concorde's sonic boom.

Pigeons have the equivalent of an in-built compass which allows them to navigate using the Earth's magnetic field and the position of the Sun. But they also need a map sense as well - a mental chart linking their starting point with their destination.

Sound barrier

Some scientists suggest that infrasound - low frequency sound waves - are involved. Californian geophysicist Jon Hagstrum - who has studied the disappearance of thousands of homing pigeons - believes the soundwaves are generated by movement in the oceans.

Pigeon BBC
Pigeons navigate using an in-built "compass"
The sea continually exerts pressure on the seabed and causes the land to shake, sending seismic shivers that are then radiated into the air. Concorde's sonic boom could have temporarily deafened the birds to infrasound - switching off their map sense.

Hagstrum, of the US Geological Survey in Menlo Park, assessed four pigeon races that he said were disrupted when the birds flew into a cone-shaped shockwave of low-frequency noise, left by Concorde when it broke through the sound barrier.

He believes steep hillsides reflect airborne sound waves horizontally, providing a unique low-frequency beacon that homing pigeons can perceive for hundreds of miles.

Bad weather

But David Glover, editor of the UK magazine British Homing World, who provided some of the data for Jon Hagstrum's study, is sceptical of the findings. He says an inquiry into the 1997 race suggested a heavy belt of rain was responsible for pushing the birds off course.

"Jon Hagstrum has calculated that the loss of these pigeons coincided with Concorde creating a sonic boom over a certain part of northern France, but I think this is a little dubious myself," Mr Glover told the BBC.

"We have good races and bad races, and we always have bad races when weather conditions are poor. If it was down to Concorde then these things would occur all the time even in good weather conditions."

The pigeon research is published in The Journal of Experimental Biology.

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