Feathers ruffled over sighting of rare bird

This is the story of Britain's most wanted. The suspect is medium-sized, of slim build with a mottled complexion and long legs. Most importantly, it has a long, thin, needle-sharp beak.

This is the story of Britain's most wanted. The suspect is medium-sized, of slim build with a mottled complexion and long legs. Most importantly, it has a long, thin, needle-sharp beak.

Operating under the name "slender-billed curlew" it leads a fly-by-night existence. Few people have spotted the suspect and those who do have been warned not to approach. After all, it is very, very rare. So rare that when a sighting was reported in Suffolk 12 days ago, it sparked an acrimonious bird hunt that is proving one of Britain's oddest wildlife detective stories.

The suspected sighting of the bird at the Minsmere bird reserve on the Suffolk coast was greeted with immense excitement among birdwatchers. It was, in the jargon, a "major twitch".

If proven, it would have been one of the most significant rare bird sightings in decades. Once common across central and eastern Europe, Numenius tenuirostris is now officially termed "critically endangered" - a bird at imminent risk of extinction. Some fear it has already disappeared.

Its last known nesting site was found in 1924, in Siberia, and none have been seen at its regular wintering grounds at Merja Zerga in Morocco since 1995. Its only previous confirmed sighting in the UK was in Northern Ireland, in 1998, but since then it has effectively disappeared. At most, says Birdlife International, the world body for ornithologists, there are fewer than 50 individuals left alive.

The sighting was so significant that the Royal Society for the Protection of Birds flew in Didier Vangeluwe, the world expert on slender-billed curlews, from Brussels. Mr Vangeluwe was convinced, and announced that it was indeed a slender-billed curlew.

But Britain's bird watchers - among the most pedantic in the world - were not so sure. The Minsmere bird, they said, was too large, its markings too similar to an ordinary curlew's, and, crucially, its beak was too thick. The message went out through Britain's twitching community - Didier is wrong.

Grahame Madge, an RSPB spokesman, explained: "What we're left with is an incredible spat: the expert says that it is a slender-billed and the British birding community isn't even bothering to look at it now. "

In a final effort to decide the matter conclusively, the RSPB is now paying for specialised "isotope tests" on two wing feathers from the Minsmere bird. This would see if they have the same radioactive "signature" as the soils from breeding grounds in Russia and northern Kazakhstan.

Plans to use DNA tests on its droppings or feathers were announced 10 days ago but quietly dropped, when it was realised that no one actually had any viable DNA samples.

John Marchant of the British Trust for Ornithology and one of the UK's authorities on coastal birds, said: "It's very rare for there to be a major controversy over a bird's identity. The stakes in this case are so high because it could indicate whether the slender-billed curlew still exists as a species, and therefore what resources should be directed at conserving it."

He is now convinced the bird has been misidentified. "People are having trouble picking it out from the other curlews that it's with," he said. "It has become less and less distinctive as it has moulted its flank feathers. Some people aren't sure they've been watching the right one."