Researchers at National Zoo work to save Hawaiian birds from extinction

Tanisha Tyson squeals, “Oh he’s pretty,” as she points to a brilliant orange bird with jet-black wing feathers and a long downwardly curving bill. On a field trip to the National Zoological Park, the first-grader from Baltimore’s George Street Elementary School has just been dazzled by a Hawaiian iiwi. Such excitement is not reserved for first-graders—glimpsing the avifauna of these Pacific islands also has thrilled Smithsonian scientists.

Tucked into the back hall of the National Zoo’s 70-year-old Bird House is an exhibit that opened in March, titled “The Birds of Paradise Lost.” It is modest by most standards. A video loop and three species of living Hawaiian birds are the highlights of this exhibit, but it is all about the work of Smithsonian scientists. “We’ve uncovered a fascinating history of the avifauna of Hawaii,” Paul Tomassoni, assistant curator of birds, says. “And we’re eager to share that information with our visitors.”

On the video, Helen James, a paleontologist at the National Museum of Natural History, ventures into one of Hawaii’s dark cavelike lava tubes. She explains her research, which began in the early 1980s with colleague Storrs Olson, a curator in the National Museum of Natural History’s Department of Vertebrate Zoology.

“You need a good light to work in these caves,” she says on the video. In an effort to reconstruct the natural history of the avifauna of Hawaii, James is seen hunting for the remains of extinct birds. It is a tedious process, she notes, because she and her research team screen all of the sediment with the hope of finding as many bones as possible. The bird bones are brought back to the National Museum of Natural History and compared with the bones of known birds in the collection.

Over the years, James’ research, along with that of other Smithsonian scientists, has revealed that the Hawaiian Islands once had a much more diverse and, in many ways, spectacular avifauna than it has today.

The Hawaiian Islands, which sprout over a “hot spot” in the Earth’s mantle, were formed by volcanic activity and were carried off to the Northwest by the movement of the Pacific Plate. As land forms go, they are geologically young and make up the most isolated island group on Earth. It is this isolation that makes the region interesting to Smithsonian scientists, who are investigating the colonization of new land by animals and looking at ways animals change over time to take advantage of these new environments.

More than 100 species of terrestrial birds once inhabited the Hawaiian Islands; however, only 35 species survive today. Based on materials unearthed by James and Olson, it appears that humans may have played a role in the mass extinction of many Hawaiian birds. Evidence to support this theory abounds, including the age of the extinct birds’ bones, as well as the cultural artifacts discovered in proximity to the bones.

Polynesians were the first to arrive on the islands some 1,600 years ago, and the first Europeans landed in 1778. The Europeans brought with them avian diseases and insects, including mosquitoes that transmitted diseases to the birds. Grazing and predatory mammals brought to the islands also took a toll on the birds. Of the 35 surviving species of birds, 24 are listed as endangered. The remaining 11 species are so reduced in numbers that conservation biologists believe they have a poor chance of avoiding extinction.

“There is no other place on Earth with so many of its birds threatened with extinction than on the Hawaiian Islands,” Robert Fleischer, a geneticist at the National Zoo, says. Fleischer and a team of biologists at the National Zoo have brought the new technology of molecular genetics to the study of Hawaiian birds.

“By using traditional methods alone, it is often impossible to understand how birds are related to each other,” Fleischer explains. “This is sometimes the case for living species, and it can be particularly frustrating when working with an extinct bird, because all you have to go on is a bone fragment.”

Building on the work of James and Olson, Fleischer has been able to plot much of the biological history of bird colonization and speciation on the Hawaiian Islands. This diversity, he says, is typical on large, old, continental land masses, but with the islands separated from the continents by thousands of miles of ocean, the question asked by the scientists is, “Where did the birds come from?”

One group of birds that Fleischer and his staff looked at was the Hawaiian honeycreeper, which exhibits the characteristics of warblers, orioles, finches, parrots, woodpeckers and honeyeaters.

Were all of these birds descendants of a single ancestral species? To answer this question, Fleischer and his staff isolated and compared honeycreeper DNA molecules taken from two sources: living birds and preserved museum specimens.

If a species changes over time and splits into two, from that point on, much of the variation that accumulates in the DNA of each of the two new species will be different, Fleischer explains. By comparing the changes in honeycreepers and other songbirds, he and his team were able to determine the relationships among the various species of honeycreepers and build a tree illustrating these relationships.

According to Fleischer, all of the more than 50 species of honeycreeper that inhabited Hawaii evolved from a single species of finch that somehow made it across the Pacific Ocean only 4 million years ago. This one species diversified into more than 50, to take advantage of the various natural resources provided on the islands. Twenty-eight of the honeycreeper species are now extinct.

Fleischer and his staff also are applying work in molecular genetics to the conservation of the remaining Hawaiian birds. For example, Cheryl Tarr, a graduate student in the National Zoo’s Molecular Genetics Lab, studied a species of honeycreeper, the Laysan finch. Using DNA analysis, she was able to document the loss of genetic variation in newly founded populations. Since this loss leaves a population less able to cope with changes in its environment, these quantified results have implications pertinent to managing the recovery of endangered Hawaiian birds.

Genetic work also is under way on avian malaria, which is carried by mosquitoes and is a major threat to the remaining indigenous Hawaiian birds. The malaria-carrying mosquitoes eliminated most of the native birds that at one time lived in the islands’ lowlands. Luckily, the mosquitoes do not survive at higher elevations, but recent evidence indicates the pest is slowly adapting to life higher up the slopes.

As a second line of defense, zoos across the country have joined together to learn how to propagate Hawaiian honeycreepers so that their husbandry might be better understood. As part of this effort, the staff at the National Zoo’s Conservation and Research Center in Front Royal, Va., was the first to breed two honeycreeper species, the iiwi and the amakihi, in a controlled environment.

The amakihi has attracted the attention of Fleischer. Unlike other native Hawaiian birds that almost always die from malaria, the amakihi exhibits resistance to the disease. Fleischer wants to find the genes that enable these birds to cope with malaria. He hopes to determine if the resistance to malaria exhibited by the amakihi is coded in an area of the DNA molecule known as the major histocompatability complex.

This DNA study is a subject of considerable interest to geneticists. In the future, it also might be possible to engineer these genes for malaria resistance into species of honeycreepers threatened by the advance of the mosquitoes.

By Mike Morgan National Zoological Park

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