John W. Fitzpatrick said there have been several independent sightings of a bird that appears to be an ivory-billed woodpecker.
A video clip of one bird, though blurry, shows key features, including the size and markings, Fitzpatrick reported.
"The bird captured on video is clearly an ivory-billed woodpecker. Amazingly, America may have another chance to protect the future of this spectacular bird and the awesome forests in which it lives," Fitzpatrick, director of the Cornell Laboratory of Ornithology, said in a statement.
Once prized by Indians who believed that its bill possessed magical powers, the ivory bill was also hunted in the late 19th and 20th centuries for its feathers, popular on ladies hats. Loss of habitat was its main threat, however.
The ivory-billed woodpecker, one of the largest such birds in the world, is one of six North American bird species thought to have become extinct since 1880. While somewhat rare, the bird ranged widely across the southeastern United States until logging eliminated many forests between 1880 and the 1940s.
Sometimes called the white-back, pearly bill, poule de bois and even Lord God bird, the ivory bill was known for the two-note rap of its bill as it ripped into tree bark in search of edible grubs and beetle larvae.
There have been anecdotal reports of the birds, but the last conclusive sighting in continental North America was in 1944 in northern Louisiana. A subspecies of the bird has been reported in Cuba.
The new sightings have been in the Big Woods region of Arkansas and each involved a different person or group, Fitzpatrick said.
About 40 percent of the forest in this region is approaching maturity, and nearby land has been reforested in the last decade.
Fitzpatrick identified the bird by magnifying and analyzing individual frames of the video clip.
With a three-foot wingspan the bird is larger than a pileated woodpecker, which is similar in appearance, and has the black-and-while markings of the ivory-billed bird.
The Nature Conservancy, which has protected a large segment of land in the area, reported that the first sighting came on Feb. 11, 2004, by George Sparling of Hot Springs, Ark.
After learning of the sighting, Tim Gallagher of Cornell and Bobby Harrison of Oakwood College in Huntsville, Ala., traveled to the area with Sparling and also sighted the bird. Other sightings followed, including one on April 25, 2004, in which David Luneau of the University of Arkansas at Little Rock videotaped the bird taking off from the trunk of a tree.
The Nature Conservancy reported 15 sightings of the bird in 7,000 hours of search time concentrating on a 16-square-mile area.