Pigeons may come to a supersonic end

Pigeon fanciers, already burdened by having to wait for the right weather and wind conditions before starting their birds' races, may have to add in another confounding factor - Concorde's flight times.

Pigeon fanciers, already burdened by having to wait for the right weather and wind conditions before starting their birds' races, may have to add in another confounding factor - Concorde's flight times.

The shockwaves created by the supersonic aircraft's engines as it breaks the sound barrier - usually over the English Channel when it leaves the UK - flummoxes the pigeons, said Jon Hagstrum, a scientist at the US Geological Society in Menlo Park, California.

As many as 30,000 birds are released from locations in France to head back to Britain every weekend in the summer. But sometimes, the birds take surprisingly long to arrive, while others simply never return.

The Royal Pigeon Racing Association, one of the sport's governing bodies, set up an inquiry after a third of the 60,000 birds released to celebrate its centenary in June 1997 were never seen again, and the rest were late. "We really didn't know why," said Peter Bryant, the association's general manager. "Then we were contacted by Dr Hagstrum."

Dr Hagstrum reckons that pigeons navigate by "infrasound" - low-frequency sound waves that animals can hear but humans cannot. Ocean waves create pressures which make the land shake, releasing infrasound that turns valleys and hills into "beacons" whose unique signals travel for hundreds of miles, he told New Scientist magazine.

But when Concorde breaks the sound barrier, it creates a shock wave that drowns out those beacons, he said.