Video analysis adds evidence for ivory-billed woodpecker

08/25/05

ITHACA, N.Y. -- On April 25, 2004, University of Arkansas researcher David Luneau accidentally kept a video camera running as his canoe drifted through a bayou in the Big Woods of Arkansas -- and recorded an ivory-billed woodpecker.

The video, blurry because the recorder was on auto focus, was the main piece of evidence featured online in an April 25 Science Express paper claiming the rediscovery of the woodpecker, once thought to be extinct.

While skeptics have refuted the video, claiming that it shows a pileated woodpecker, Cornell University researchers are standing firmly by the video as evidence of the existence of the ivory-billed woodpecker.

Ken Rosenberg, director of the Cornell Lab of Ornithology's Conservation Science Program, offered a frame-by-frame analysis of Luneau's video at the American Ornithologists' Union Meeting at the University of California-Santa Barbara, Aug. 24.

Rosenberg reviewed the researchers' rationale for claiming that the video captured an ivory-billed woodpecker. Though blurry, the video shows the bird's outlines and black and white coloring, he said.

The main difference between ivory-billed and pileated woodpeckers is in the placement of the black and white coloring, especially on the wings, and accounts for why an untrained eye may easily mistake a pileated for an ivory-billed woodpecker.

On an ivory-billed woodpecker, white feathers run along the trailing back edges of its spread wings, while black feathers trail along a pileated woodpecker's wings, from the bird's body all the way to its wing tips. Rosenberg showed frames from the Luneau video, indicating that only white feathers were visible along the broad trailing edge of both the underwing and upperwing.

To show the differences, the video frames were compared with blurry frames of pileated woodpeckers.

Also, using models of ivory-billed woodpeckers, scenes were reenacted with an out-of-focus camera, revealing a striking similarity to the actual video. Frames from a video of a pileated woodpecker model were shown for comparison.

Other evidence is that in one segment of the Luneau video, a large bird partially peeks out from behind a tree trunk, showing a portion of its white wing. Researchers from the Lab of Ornithology placed a stuffed ivory-billed woodpecker on the actual tree where the video was shot to show that the white corresponds to the white outer wing of the perched bird. Still, skeptics claimed this could be the underwing of a pileated woodpecker extending from behind the trunk and revealing white feathers.

To counter this claim, Lab of Ornithology members in Arkansas physically measured the tree trunk that appeared in the video, Rosenberg explained. They also measured a roosting cavity from a 1935 photo of an ivory-bill. Using the actual tree trunk and cavity, which the lab has in its possession, the researchers were able to take the relative measurements from the images and make absolute measurements of the bird's wings.

While the distance from the pileated woodpecker's wrist (part of the ulna, one of the wing bones) to tail-tip measures 29 centimeters (11.4 inches) on average, the wrist-to-tail tip distance in the video reaches a full 35 centimeters (13.8 inches), which is in the upper range for ivory-bills. The size of the wing ruled out that the frames were of a pileated woodpecker, Rosenberg said.

When one audience member asked about sightings of pileated woodpeckers with extra white on their wings, Rosenberg said that he and his colleagues were aware of molting pileated woodpeckers that lose some of their black feathers, revealing more white. But, he added, he has never heard of such molting occurring symmetrically, as the wings in the Luneau video appear.

"We think the body of evidence confirms the presence of at least one ivory-billed woodpecker," said Rosenberg.

Source: Eurekalert & others

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