PENSACOLA, Fla. (AP) -- After spending months in remote northwest Florida swamps searching for the ivory-billed woodpecker, researchers say they have seen and heard the rare bird once believed to be extinct.

But Auburn University ornithologists, who published their findings in Canada's Avian Conservation and Ecology journal online Tuesday, failed to capture a picture of the large woodpecker, which makes a distinct double rapping sound.

That lack of evidence means doubt about the bird's return remains.

The bird was thought to be extinct until 2004 when Cornell University researchers released recordings and an inconclusive grainy video after searching for it in the swamps of eastern Arkansas. The last confirmed ivory-billed sighting was in 1944.

Auburn ornithologist Geoffrey Hill headed the four-month Florida search that ended in April. He said his team would return to the Choctawhatchee River basin sometime around November with better equipment to try to get photographs.

"On 41 occasions different team members have seen the bird. We heard that double knock, it's a sound the ivory-billed makes that no other bird makes, but we didn't get a clear video of the bird,'' Hill said.

"I think people should be skeptical. I think they should demand clear photographic evidence. I might start to get skeptical myself thinking, 'I've seen this bird,' but how could I have seen a bird that it is impossible to photograph,'' he said...