Photo courtesy of Kent Woodruff
A vinyl tag identifies Eagle 166, which started life in Montana.

Raptor institute tracks Golden Eagle’s movements

By Marcy Stamper

An 8-year-old male Golden Eagle from Montana has been enjoying a winter retreat in the Methow Valley, spotted in early January near Beaver Creek and then in mid-February feeding on a carcass near Gold Creek.

Golden Eagles are typically faithful to their winter territory, so it is unusual that the bird has traveled so far from western Montana, where it was last seen in January 2013, according to Rob Domenech, executive director of the Raptor View Research Institute in Missoula. The bird, dubbed Eagle 166, is identifiable because the raptor institute outfitted it with a large blue-and-white numbered wing tag easily visible from a distance.

Eagle 166 may be a year-round resident in the Methow, or it may be spending only its winters here and then migrating to summer breeding grounds in northern Canada or Alaska, said Domenech.

Tagging the birds assists with conservation and management, providing information about the birds’ territory and migration routes, he said.

Photo by Rebecca Walker-Vaughan
Eagle 166 was spotted near Gold Creek in February.

This information helps scientists understand the impacts of infrastructure — such as oil, gas and wind-energy development — on the birds. Industrial wind turbines have a significant impact because Golden Eagles take advantage of strong winds to travel long distances with a minimum expenditure of energy, said Domenech.

The raptor institute uses wing tags because they can supply information about birds as they move around, whereas more traditional leg bands are tracked only when birds are captured or if they die. The Golden Eagle project has documented re-sightings from Mexico to the Brooks Range in Alaska, said Domenech.

With an online registry of the wing tags — the project has tagged more than 300 Golden Eagles over the past 13 years — anyone can easily find out about a bird and provide information on a sighting to the raptor project.

That’s what Rebecca Walker-Vaughan did when she snapped photos with her phone of Eagle 166 on the South Fork of Gold Creek on Feb. 16. Wildlife biologist Kent Woodruff photographed the bird on Upper Beaver Creek on Jan. 4 and also reported the sighting.

“I would expect the bird will be there [in the Methow] in future years,” said Domenech.

There is a 50- to 60-percent chance of a winter encounter with a tagged bird, whereas there’s only a 7-percent chance of seeing a banded bird again — and the majority of those are found dead, said Domenech. Many encounters are photos taken by wildlife cameras.

Eagle 166 was initially tagged at a ranch used by the raptor project just south of Missoula on Feb. 15, 2012, and then found there again on New Year’s Day the following year. In those instances, the raptor institute used bait to lure the bird.

The vinyl tags weigh 13 grams. They have been used for years in projects that monitor raptors and other species such as condors, said Domenech.

Researchers are able to determine an eagle’s age from its plumage until it is 5 years old. When first tagged in 2012, Eagle 166 weighed 8 pounds, 4 ounces. It’s not uncommon for a Golden Eagle to have a wing span of 7 feet. They can live up to 30 years in the wild, said Domenech.

Golden Eagles typically use a territory of about 100 square miles when they are breeding, but sub-adults might travel further looking for a good place to settle. A high-density area could have a nest every few miles, said Domenech.

“Once an area is an eagle territory, it’s always an eagle territory,” until it can no longer support a pair or enable the birds to raise their young, said Domenech. There are nests in the Rocky Mountains that are more than 1,000 years old, used by successive generations of birds, he said.

For more information or to report future sightings, contact the Raptor View Research Institute at (406) 258-6813 or rob@raptorview.org. The website is www.raptorview.org.