MELISSA BLOCK, host:
Sometimes scientific debate can resemble a poker game. Take the case of the ivory-billed woodpecker, the American bird long thought to be extinct. Biologists said last April they had found one. Then last month another group of experts challenged that claim. They said the evidence wasn't good enough. Now the discoverers have shown some more of their cards, and the doubters have dropped their challenge. NPR's Christopher Joyce has the latest on the woodpecker debate.
CHRISTOPHER JOYCE reporting:
The original claim last April hung on a four-second video and a handful of sightings in a swampy maze of bayous along Arkansas' White and Cache rivers. The Cornell University Laboratory of Ornithology and The Nature Conservancy published their evidence in the journal Science. They expected a debate. Last month they got it. Yale University biologist Richard Prum and two other experts said they were not convinced, and they said they would publish their doubts. Now the challengers are withdrawing their paper. Prum says he's changed his mind after hearing startling audio recordings from Arkansas. The Cornell team made them over the past eight months, but they haven't released them publicly. Prum says they capture the sound of an ivory bill.
Mr. RICHARD PRUM (Biologist, Yale University): The recordings we've heard include kent calls, some of the distinctive vocalizations, and a series or a pair of double rap notes between two individual birds, one farther away from the microphone and one closer in, apparently answering one another.
JOYCE: The kent call is the ivory bill's vocalization. It's sometimes described as the sound of a toy trumpet. Prum and other bird biologists know it from the only known recording of an ivory bill made in 1935, also by a Cornell team. This is the recording of the kent call.
(Soundbite of kent call)
JOYCE: The Cornell team actually used this 70-year-old recording in an experiment in Arkansas this summer. They played the 1935 sounds loudly in the forest. Tim Gallagher is a member of the Cornell team.
Mr. TIM GALLAGHER (Cornell University): We broadcast them to see what the sounds sounded like when they'd gone through a distance, through foliage and trees and everything. And those sound extremely similar to the kent calls picked up from the White River.
JOYCE: Cornell's latest Arkansas recordings also include double raps. Woodpeckers often rap on a tree to signal other woodpeckers. North of Mexico, only the ivory bill was known to make a rapid double rap, something like this.
(Soundbite of double rap)
JOYCE: Like the kent calls, the raps were picked up by one of 24 recording devices attached to trees. Prum agrees with the Cornell team that the kent calls are so distinct they're not likely to be confused with other forest sounds. And the two birds rapping back and forth also makes it unlikely their sounds were made by snapping branches, gunshots or other animals. Cornell scientists say they wouldn't be surprised if other doubters do come forward. But for now, says Yale's Richard Prum, he's no longer one of them.
Mr. PRUM: We're really excited about the evidence that the bird exists, and as a lifelong bird watcher, I shared that excitement from the beginning. I just was more skeptical than most.
JOYCE: The Cornell team is still sifting through thousands of hours of recordings. The bird sounds they've identified so far have come from two distinct areas, which suggests two populations. Christopher Joyce, NPR News.
MICHELE NORRIS (Host): You're listening to ALL THINGS CONSIDERED from NPR News. Transcript provided by NPR, Copyright NPR.
