Study seeks to track movements of eagles that winter on Skagit River

SKAGIT COUNTY -- Each winter like clockwork, hundreds of bald eagles flock to the Skagit River here to feed on carcasses of chum and coho salmon that have returned to spawn.

But despite years of observing the birds along the river, biologists say the answer to a seemingly simple question has eluded them: Where do the majestic raptors come from?

"At the moment, we really can't say with any degree of certainty where these birds hail from," said Bob Everitt, who oversees northern Puget Sound operations for the Washington Department of Fish and Wildlife.

"That's a big question, and one we hope to soon be able to answer," he added.

State wildlife biologists currently are working to trap a small number of the adult bald eagles that winter along the river and strap small, rectangular radio transmitters to their backs. The transmitters will send signals to satellites capable of pinpointing the birds' movements once they leave the river.

Ultimately, biologists hope to determine where the birds go to nest and breed, said Jim Watson, the wildlife biologist heading up the experiment. This information, in turn, will be used to figure out what types of fishing, rafting and other activities can occur along the river without disturbing the eagles and their feeding habits.

For decades, bald eagles, which are classified as a federal and state threatened species in Washington, have been known to return to the scenic Skagit River from mid- November through mid-March.

Up to 500 eagles the largest concentration in the lower 48 states have been estimated to winter along the river, perching or roosting in the cottonwoods and old timber that line its shores.

The eagles have long shared the river with all types of recreationists, most notably birdwatchers and anglers. The latter are attracted to the river because of its excellent steelhead fishing, which typically begins in late November or early December and lasts until spring.

In recent years, concerns have been voiced by state and federal natural resource officials, environmentalists and others over the increasing level of recreational and commercial activity occurring on the river. They fear the activity may be disturbing the eagles, making it difficult for them to feed.

These concerns prompted the Department of Fish and Wildlife and the Nature Conservancy in the mid-70s to purchase some land along the river above the small community of Rockport to protect roost and perch trees. Since the mid-80s, the department also has requested that rafters stay off the river until after 10 a.m. to minimize disturbances to eagles.

In addition, the U.S. Forest Service, which manages the stretch of river where the eagles feed, recently began requiring commercial rafters and fishers to obtain a permit to operate on the river. Last year, the federal agency requested that all user groups voluntarily refrain from using a certain stretch of the river during certain times to protect the eagles.

The voluntary closure, which was extended to include this year, requests that user groups stay off the river between the Rockport and Marblemount bridges from 5 a.m. to 11 a.m., seven days a week. The closure will remain in effect until Feb. 28.

State wildlife officials are optimistic that the experiment now underway will eventually help determine what regulations may be needed in future years to protect the wintering eagles.

"If we find out, for instance, that the birds are coming from healthy breeding populations, the information could be used to decrease regulation of boats and rafts on the river," Department of Fish and Wildlife biologist Steve Negri said.

"On the other hand, if we learn the eagles come from depressed populations, the information could be used to increase the regulation of boats and rafts using the river during the winter months," he said.

Negri said biologists typically try to trap the birds during the morning hours when they are feeding. Fish carcasses are placed on shore, and on the rivers' sand and gravel bars, to lure birds into one of several types of traps.

Only birds that are four- to five-years-old, or breeding adults, will be outfitted with transmitters. Such birds are easily identified by the white feathers that cover their heads and tails.

Younger eagles do not return to the same nest every year to breed, and therefore would not provide biologists with the data they are seeking, Negri said.

From mid-November through early January, biologists had managed to trap 10 eagles, but only four were old enough to be outfitted with transmitters. Biologists eventually hope to put transmitters on 15 eagles as part of the study, which is being funded by the Department of Fish and Wildlife, the U.S. Fish and Wildlife Service and the U.S. Forest Service.

"Patience, lots of patience, is obviously the key in getting this experiment off the ground," Negri said.