ScienceWatch

It's All There In Black and White

    The announcement last year that an Ivory-billed Woodpecker (Camphephilus principalis) was sighted in the Big Woods of Arkansas set the entire birding world aflight - see - ScienceWatch - Another Elvis Sighting? - Even Better! (May 2005). That report from a group headed by John Fitzpatrick of the Cornell Laboratory of Ornithology, Cornell University, Ithaca, NY, claimed several individuals had seen an Ivory-billed Woodpecker, and also presented a blurry, four-second video purporting to show the bird, partially hidden, on a tree trunk and taking flight as the viewer approached.

    Now exactly a year later experts are in dispute over the interpretation of the video, shot from a canoe 60 feet away, which is the only objective evidence presented by the Cornell group. In an excruciatingly detailed analysis presented in the March 17, 2006 issue of Science, a group of biologists headed by David Sibley (yes, that Sibley) argue that the blurry black and white wing of the bird in the video is most likely that of a Pileated Woodpecker (Dryocopus pileatus).

    Sibley et al., focus on a few dozen frames showing a white patch on a black wing in a side view of the bird on the tree trunk. The Cornell group concluded these frames show the woodpecker with its wings folded and that only an Ivory-billed Woodpecker could present such a white patch on its folded wingtip. However, the Sibley group rejects that interpretation and claims the frames actually show the lining of an uplifted wing just as the bird takes off. Since both birds have extensive white patches on the underside of the wings, they say the Cornell group mistook a Pileated Woodpecker for an Ivory-billed Woodpecker.

    Using photos of a mounted Ivory-billed Woodpecker specimen on a tree trunk to make their point, the Sibley group says the size and shape of the white patch associated with the perched bird in the video better matches that of the underside of a Pileated Woodpecker wing. They also present drawings by Sibley to show that the white patches appearing in the video as the bird takes flight are more like those on the wing lining of a Pileated Woodpecker. Although they conclude that the images in the video can best be explained to fit that of a Pileated Woodpecker and not an Ivory-billed Woodpecker, they end their report rather wistfully with, “Ivory-billed Woodpeckers may persist ..., and we believe that conservation efforts on their behalf should continue”.

    The Cornell group counters with a response in the same Science issue. They say the Sibley group is mistaken in its interpretation. They also use photos of a mounted Ivory-billed Woodpecker specimen to show that the wing is indeed initially folded and that the white patch of the perched bird in the video matches that seen on the folded wing of an Ivory-billed Woodpecker. Moreover, they say that The Sibley Guide to Birds shows too much white in the Pileated Woodpecker under wing. This, they contend, erroneously led the Sibley group to think the bird in the video was a Pileated Woodpecker. They conclude that the white under wing patch of a Pileated Woodpecker does not look like that shown in the video, but rather best matches that of an Ivory-billed Woodpecker. Finally, they present frames from a video taken of life-sized models with flappable wings of both woodpeckers in flight to demonstrate that the white patch seen in the video when the bird takes off is more like the under wing of an Ivory-billed Woodpecker than a Pileated Woodpecker.*

    This controversy will continue until either more convincing evidence persuades the experts that the Ivory-billed Woodpecker truly exists or until enough time has gone by without convincing sightings so that the experts can agree that the Ivory-billed Woodpecker is indeed extinct. Right now the birding world is holding its collective breath, hoping for clear visual proof. Perhaps you would like to grab your camera and trek through the mosquito-infested bayous of the Cache River National Wildlife Refuge to join in the search?

*You may view the video and its analysis by the Cornell group at www.birds.cornell.edu/ivory/rediscovery/support.

Saul Scheinbach

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