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Eagles “Tagged” From Fallen Feathers

DNA “fingerprinting” has become a reliable way to identify individual humans or animals. A biological sample such as blood, semen, or hair can be matched to an individual.


Eastern imperial eagle chick in Kazahkstan picture courtesy Andrew DeWoody

In the world of bird research a DNA match can be made with a feather. Each feather found in a nest or on the ground can be mapped back to the individual that shed it, much like a sampling of scat can be used to identify individual leopards, wolves or other animals.

Purdue University researcher Andrew DeWoody gathers feathers shed by endangered eagles, a technique that yields plenty of information about them.

Andrew DeWoody studies eagles by using DNA in their feathers to track their movements and habits. This technique allows DeWoody to study larger populations and prevents injuries to birds because they aren’t captured.

Purdue Agricultural Communication photo/Tom Campbell

“Many birds are small, easy to catch and abundant,” said DeWoody, professor of genetics, in a Purdue University news release. “With eagles, the effort can be 100 to 1,000 times greater than catching chickadees.”

“Eagles can be hard to find, they often require live bait to attract and, with sharp talons and beaks capable of snapping off human fingers, they pose a risk to their would-be captors,” DeWoody added.

“Instead of catching eagles, DeWoody collects their feathers and uses the small amount of DNA in them to create a tag that corresponds to a particular bird. Those tags can be used to determine population, parentage, roosting patterns and sex ratio.”


DeWoody’s research method is described in a chapter of the “Handbook of Nature Conservation : Global, Environmental & Economic Issues” (Nova Science Publishers, July 2009) which was released this week. The chapter is a compilation of his research on the topic.

“In an afternoon, you can go out and pick up hundreds of feathers,” DeWoody said. “As field work goes, it’s about as easy as it gets.”

Most birds are studied by catching them in nets and attaching tracking devices. Researchers can then follow the birds and use radio technology to triangulate their locations.

Eagles and other large birds present several challenges, however, even beyond catching them.

“Eagles will literally fly hundreds of miles in two days,” DeWoody said. “They fly in areas where you can’t track them in a pickup truck.”

Capturing a bird as large as an eagle can often be traumatic to the animal.

“They’re wild animals that don’t want to be caught,” DeWoody said. “They can get hurt as well.

“Using feathers, you avoid all that.”

Costs can be as high as U.S. $5,000 for the tracking technology that researchers must attach to eagles, a prohibitive cost if studying more than a few birds.


DeWoody’s studies were done in Kazakhstan with eastern imperial eagles, a top predator of international concern because its population is declining. A 2006 field trip to Kazakhstan to gather and study the bird’s feathers was funded in part by the National Geographic Society’s Committee for Research and Conservation. (Photos DeWoody made of eagles in Kazakhstan are above and below.)

“The feathers give a good picture of recent eagle habits because they do not survive long in Kazakhstan’s winters,” Purdue said. “Any feathers collected after the winter thaw, then, had to have been recently dropped.

“In one study, DeWoody’s team found that an area thought to have about 40 juvenile eagles living in it based on human observation actually had closer to 300.”

The work also helped researchers understand more about the roosting habits of some eagles that use a nest for months at a time versus others who float around from roost to roost.

Another study showed that DNA could be used to distinguish eagle species from one another, and that imperial, golden and white-tailed eagles often utilized the same roosts at the same time.


Eastern imperial eagle chick in Kazahkstan picture courtesy Andrew DeWoody