Related Resources
The Search for the Ivory-billed Woodpecker, at Cornell Laboratory of Ornithology
Consortium for the Barcode of Life, based at the National Museum of Natural History
Spotlight on Zoo Science
June 27, 2006
Barcodes for Ivory-billed Woodpeckers
National Zoo and National Museum of Natural History scientists discover a new tool to identify some spectacular—but possibly extinct—birds.
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| Ivory-billed woodpecker. Painting by Mark Bowers/USFWS. |
Sightings of an ivory-billed woodpecker in Arkansas’s Cache River National Wildlife Refuge created a sensation when they were reported by the Cornell Laboratory of Ornithology in 2005. A few seconds of video showing a bird with tell-tale ivory-bill characteristics taking off from the trunk of a tupelo tree, re-played around the world, seemed to confirm that this legendary bird, believed to have been extinct in its native southeastern United States forests, still existed. Read the report in Science and watch the video.
Conservationists and bird lovers cheered, dubbing the bird a “lazarus species.” Since then, though, some ornithologists have disputed the evidence of the video, suggesting the bird could be a pileated woodpecker.
While the quest to find more of these elusive birds continues, scientists Rob Fleischer, of the National Zoo and National Museum of Natural History, and Carla Dove, of the National Museum of Natural History, along with colleagues from five other institutions, have found a way to tell whether feathers or feces collected in the wild come from an ivory-billed woodpecker or some other species.
At the same time, they clarified the relationships among North American ivory-billed woodpeckers, Cuban ivory bills, the imperial woodpecker of Mexico, and other woodpeckers classified in the same genus, Campephilus. (Campephilus means “lover of grubs,” a reference to beetle larvae, one of the woodpeckers’ favorite foods.)
The scientists took small skin samples from the toe pads of museum specimens of imperial woodpeckers and North American and Cuban ivory-billed woodpeckers, and extracted DNA from each. The resulting genetic sequences clearly differed among the three woodpeckers, each creating a unique pattern that can be read like a barcode. These same barcodes will appear in other biological samples, such as feces and feathers, enabling scientists to confirm or deny that a sample collected in the wild belongs to one of these woodpeckers. Consortium for the Barcode of Life, based at the National Museum of Natural History
Their results, reported in 2006 in the journal Biology Letters, also clearly showed that the North American and Cuban ivory-bills are distinct species, contrary to their current classification as a single species divided into two subspecies. In fact, the two groups differ so slightly in plumage and size that one biologist suggested Native Americans relatively recently introduced the birds to Cuba. These new genetic findings refute this idea, showing that the two split sometime between about 800,000 and 1.6 million years ago.
Further, these two species plus the imperial woodpecker, which appears to be about equally related to both, form a distinct “clade.” (A clade is any group of organisms that includes the most recent common ancestor of all those organisms and all the descendants of that common ancestor.)
All but one of the seven other Campephilus woodpeckers they tested form another clade. The outlier, the crimson-bellied woodpecker, may be a descendant of the common ancestor of both clades. The genetic evidence suggests that Campephilus woodpeckers arose in South America, where most of the 12 species still live, and moved into North America after the Isthmus of Panama formed, about three million years ago.
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| This "phylogram" shows the relationships among Campephilus woodpeckers based on this genetics study. Adapted from Figure 1 in Fleischer et al, 2006. |
The imperial woodpecker resembles the ivory-bills, but is as much as 20 percent larger—the largest woodpecker in the world, if it still exists. All three of the spectacular northern Campephilus woodpeckers are, at the very least, in dire straits.
Like the North American ivory-billed woodpecker, the Cuban ivory-bill and the imperial woodpecker saw much of their forest habitats disappear in the last century thanks largely to uncontrolled logging and other forms of habitat destruction. The last definitive sighting of a Cuban ivory-billed woodpecker was in the late 1980s. An extensive search of its last known location in 2002 came up empty, and experts agree that it is almost certainly extinct.
The last definitive sightings of imperial woodpeckers were in the mid-1950s, with some scattered reports through the mid-1990s but none by experts. Even if a bird or two still survives, it seems inevitable the species will go extinct. If, as the recent sighting suggests, a few North American ivory-bills are still pecking for grubs in the forests of the southeastern U.S., there is a chance for the species to rebound. Their forest habitats have recovered somewhat and large blocks of forest are now protected. In contrast, there are no protected areas in what scraps remain of the imperial woodpecker’s Mexican habitat.
Still, conservationists are reluctant to give up hope and now, thanks to Fleischer, Dove, and their colleagues, there is a new tool for verifying the existence of these birds—even if no one is lucky enough to see one.
Fleischer, R. C., J. J. Kirchman, J. P. Dumbacher, L. Bevier, C. Dove, N. C. Rotzel, S. V. Edwards, M. Lammertink, K. J. Miglia, & W. S. Moore. 2006. Mid-Pleistocene divergence of Cuban and North American Ivory-billed Woodpeckers. Biology Letters, in press.
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