Woodpecker's existence questioned

The last confirmed sightings were in the '30s and '40s

Further doubt has been cast on the claim that a bird long-thought extinct is alive in North America.

Fleeting video footage of what many experts believed to be an ivory-billed woodpecker was captured in 2004 in an Arkansas swamp.

But since then, searches have failed to find any hard evidence for the bird.

Now, Aberdeen University's Dr Martin Collinson has told the journal BMC Biology that the video may simply show a pileated woodpecker in flight.

Dr Collinson has re-analysed the footage and says the bird in the pictures appears to have black trailing wing edges rather than the unique white features associated with the ivory-billed woodpecker (Campephilus principalis).

The videoed bird also appears to flap its wings at the rate a pileated woodpecker (Dryocopus pileatus) would - 8.6 times per second.

Format fooling

"A poor quality video of pileated woodpeckers can look like ivory-billed woodpeckers - and in that respect it can catch an observer out; and a mistake can be made. And in this case, I think a mistake has been made," Dr Collinson told BBC News.

The Aberdeen researcher also argues that the missing bird's large size and colourful plumage would surely have been seen by now in the many follow-up surveys.

"The ivory-billed woodpecker isn't some small brown bird that can only be identified by one in a thousand; it's an enormous black and white bird with a red head," argued Dr Collinson.

"OK, these swamps are pretty remote, but there are hundreds of people in there, right now, looking for the ivory-billed woodpecker. Eventually these birds would turn up."

But others still hold to the idea that the video did indeed show an ivory-billed woodpecker.

John Fitzpatrick, a director of Cornell University's Laboratory of Ornithology, said that different formats of the footage resulted in "comparing apples to oranges".

He told the Associated Press that Dr Collinson's evidence about similarities in the birds' colouring, wing patterns and flight patterns were skewed as a result.

Robot hunt

Can an automated search find the lost bird? Robot looks for woodpecker

When the 2004 video was released, it stunned ornithologists worldwide, with some comparing the discovery to finding the dodo.

It ignited hope that other extinct birds might be clinging on to survival in isolated places.

The last confirmed sighting was in 1944.

Researchers hope robot bird-watchers may yet have the final say. Automated cameras have been set up in the Big Woods refuge of Arkansas to continue to spy for the elusive creature.

"I am happy to be proved wrong; a good photo would end this debate," said Dr Collinson.

"I would be delighted; I would love to see an ivory-billed woodpecker."