Academy Research: Birds of a Feather?

These two Ivory-Billed Woodpeckers were collected in 1894 and now reside in the Academy’s ornithology collection. Nearly 70 percent of the museum's 92,000 bird specimens were collected prior to 1925, making the collection a very valuable resource for historical data.
These two Ivory-Billed Woodpeckers were collected in 1894 and now reside in the Academy’s ornithology collection. Nearly 70 percent of the museum’s 92,000 bird specimens were collected prior to 1925, making the collection a very valuable resource for historical data. Photo: Dong Lin
Through DNA testing, Academy ornithologist Jack Dumbacher has found that some birds previously assigned the same name are actually separate species.

Two birds fly through the jungles of Papua New Guinea, sporting very similar plumage. Although they have historically been classified as two members of the same species, they inhabit separate parts of the island, and recent DNA testing has shown that they share only 92 percent of their genetic code. These two animals are therefore twice as different from one another as humans and chimps, which are a 96 percent genetic match. Clearly, this new data indicates that the birds should be reclassified as two distinct species. What may not be as readily apparent, at least to non-scientists, is why a known bird receiving a new name should be a noteworthy occasion.

“Biodiversity is disappearing from our planet at an astonishing rate,” says Academy curator Dr. Jack Dumbacher. “If we’re going to make informed decisions about how to halt that trend, we need to understand how biodiversity is distributed across the planet. Accurately naming new species and subspecies helps us to create a more meaningful map of biodiversity distribution.” It is also a necessary prerequisite for achieving legal protection for threatened habitats in the United States. No legislation has ever been passed that directly protects endangered habitats or ecosystems. However, because of the Endangered Species Act of 1973, it is possible to protect individual species, subspecies, and distinct population segments. Under this legislation, habitats can also be protected if they are deemed essential for the recovery of an endangered species. Thus, the process of finding, naming, and mapping new species has taken on additional importance over the past few decades.

This is precisely the type of work that Academy scientists do every day, both by conducting fieldwork around the world and by analyzing the roughly 20 million specimens in the museum’s research collections. In recent months, Dumbacher has discovered new species of birds through both his fieldwork in Papua New Guinea and his work with the Academy’s collection of avian specimens, which includes over 92,000 skins, skeletons, nests, eggs, and tissue samples.

Located almost directly on the equator, Papua New Guinea is the largest tropical island in the world. Although it contains less than 1 percent of the planet’s land, it houses 8 percent of the known species of birds. For the past several years, Dumbacher has been working to create an accurate distribution map of these birds across the island, focusing his efforts on six species whose members seemed to display a high degree of variation. By conducting DNA analysis on samples from hundreds of birds around the island, he found that three of these species should probably be broken up into a total of 11 or 12 separate genetic species. “It turns out that some of the birds that were previously grouped together in the same species had more genetic variation than entire genera of birds in North America,” Dumbacher explains. “Within a species, you generally see less than 2 percent variation between individuals. But the birds categorized as Variable Pitohuis in New Guinea had up to 8 percent sequence divergence.” Barred owlet-nightjars and little shrike-thrushes also contained enough genetic variation to warrant separation into multiple species.

The new species distribution maps that Dumbacher has created for New Guinea’s birds will help inform future conservation decisions in the country. Meanwhile, his work with the Academy’s specimen collection is helping to inform the recovery efforts for a species closer to home.

An American legend, the Ivory-Billed Woodpecker is a large, showy bird that reportedly went extinct when the bottomland forests of North America were logged. For over 60 years, scientists searched unsuccessfully for a surviving member of the species. Then, in 2004, an Ivory-Billed male was photographed in eastern Arkansas. This sighting, along with recent reported sightings in Florida, has sparked hope for the recovery of the species, which was once found throughout much of the southeastern United States and in the forests of Cuba. Because the birds are elusive and extremely rare, finding fallen feathers may be one of the easiest ways to track them. In order to definitively identify any feathers they may find, however, scientists must be able to match the DNA from those feathers to DNA from Ivory-Billed Woodpecker specimens. Therefore, Dumbacher teamed up with colleagues from five other museums and universities to establish a DNA databank for Ivory-Billed specimens that were collected in the late 19th and early 20th century.

Dumbacher and his colleagues were able to extract DNA samples from ten Ivory-Billed Woodpecker specimens, two of which are housed in the Academy’s ornithology collection, by taking small snippets of toe pad tissue from each of the valuable specimens. They also tested the DNA from three Imperial Woodpeckers, the closest living relatives of the Ivory-Billed birds. The resulting data showed that the Ivory-Billed Woodpeckers in North America and Cuba were actually just as different from one another as each of them was from the Imperial Woodpecker. “We realized that we were actually looking at two separate species of critically endangered birds, at least one of which may very well be extinct, since Ivory-Billed Woodpeckers haven’t been documented in Cuba in decades,” says Dumbacher.

Until this data was published, many scientists believed that humans introduced Ivory-Billed Woodpeckers to Cuba relatively recently and that the birds had not been isolated on the island long enough to evolve into a new species. However, the DNA data collected by Dumbacher and his colleagues indicates that the North American and Cuban Ivory-Billed Woodpeckers diverged from one another nearly a million years ago and now have distinctly different DNA.

These findings have important implications for the management of any remaining Ivory-Billed Woodpeckers. Scientists now know that if a Cuban bird is found in the future, interbreeding efforts between the North American and Cuban cousins would probably not be fruitful. They also have a definitive way to assess whether any potentially significant feathers that may be found belong to the rare Ivory-Billed Woodpecker or the more common Pileated Woodpecker. This new ability to track the birds through their feathers will help conservation managers decide which habitats are most important to protect for the survival of the species.