In the strongest published criticism yet of claims for the sighting of the ivory-billed woodpecker in Arkansas in 2004, an ornithologist who was not involved in the search has called claims for proof of the bird's existence "faith-based ornithology."
The ivory bill was, or is, the largest North American woodpecker. It inhabited Southeastern forests that have been heavily logged, and the bird had been thought extinct, although occasional unconfirmed sightings have occurred often since the last confirmed one in the middle of the last century.
Then, in the spring of 2005, scientists announced that the bird had been found in the Cache River National Wildlife Refuge in Arkansas, prompting a surge of elation among birders and the general public, and later a steady current of questions and skepticism.
Jerome A. Jackson, an ivory bill specialist at Florida Gulf Coast University in Fort Myers, has now increased the intensity of the discussion in a 15-page article in the current issue of The Auk, a quarterly ornithology journal published by the American Ornithologists' Union. In the article, Dr. Jackson writes of a "rush to publication" of the article in Science, published online in April 2005, that reported the 2004 sighting.
He also criticizes publicity about the sighting by conservation organizations and the Interior Department as the "selling" of the ivory bill and says the bird's existence has not been confirmed.
The strongest piece of evidence in the Science paper is a brief, blurry videotape that Dr. Jackson says shows a pileated woodpecker, not an ivory bill.
John W. Fitzpatrick, head of the Cornell Lab of Ornithology in Ithaca, N.Y., coordinator of the search and announcer of the discovery of the ivory bill, said in an interview after he had read Dr. Jackson's article that he stood by the paper in Science.
Dr. Fitzpatrick said, "I have not yet seen any detailed scrutiny of the video that disproves our case."
He said that what "hurts the most" is Dr. Jackson's accusation that the Cornell Lab and other groups had been "selling" the ivory bill to promote conservation and that this effort had taken over the science. "We've tried very hard not to oversell what we know," Dr. Fitzpatrick said.
The search is continuing at Cache River and the White River National Wildlife Refuge in Arkansas.
Dr. Fitzpatrick said the goal of the search, run by his lab, was to find a roost hole or evidence of a breeding pair. "We are still waiting for the prize," he said. "We have had a handful of moments when observers have seen what they are pretty sure is the bird. We don't have the next big clue, which is a roost hole."
Dr. Jackson said in an interview: "I am in no way saying that ivory bills are not out there. I really hope they are." But he added that he had not yet seen convincing evidence.
Richard O. Prum, at Yale, another ornithologist who is not part of the Cornell Lab effort, said he was watching the search with great interest. Last summer, he, Dr. Jackson and Mark B. Robbins of the University of Kansas wrote a critique of the Science paper. They submitted it for publication and then withdrew it as other evidence of the ivory bill accumulated, although they remained critical of the evidence in Science.
"I think the ball is in their court," Dr. Prum said. "I think they understand that to be universally accepted they're expected to find solid evidence and repeatable evidence of the bird this field season."