Have reports of woodpecker's revival been exaggerated?

But now another expert is raising doubts about the sighting and says the grainy video purporting to show the ivory-billed woodpecker is far from conclusive. "No one wants to find this bird more than me," Jerome Jackson, the professor of Zoology at Florida Gulf State University, told The Independent.

"But the evidence thus far is simply not conclusive ... That's not the way science works. What we have at the moment is hope. We now have to go out and find the truth."

The "rediscovery" of the bird, whose last confirmed sighting took place in 1944, was announced last April by researchers at Cornell University, New York, who reported their findings in the journal Science. They pointed to several independent sightings of the bird as well as the video clip they said showed key features of the woodpecker, including its distinctive wing markings.

Mr Jackson, the author ofIn Search of the Ivory-Billed Woodpecker, published last year, will detail his doubts in a forthcoming paper to be published by the Public Library of Science Biology, an online British-based journal.

At the moment the paper is going through the review process, which includes giving the team from Cornell the opportunity to prepare a rebuttal. Connie Bruce, a spokeswoman for Cornell's ivory-billed woodpecker project, said challenges from other biologists were routine. "We would have been disappointed if there was no close scrutiny by the scientific community," she said.

The Nature Conservancy, which was part of the group that announced the woodpecker's return, is standing behind its findings. Jay Harrod, a spokesman, said: "One of the reasons that we kept this story a secret for so long was because we didn't want to present it until the analysis of the video had been completed."

Since the woodpecker's rediscovery, federal agencies have promised to spend millions of dollars to help preserve the bird's eastern Arkansas habitat in and around the Cache River National Wildlife Refuge.