Migrating With the Golden Eagles of Denali

Carol McIntyre has seen the world from an eagle's perspective. A biologist for Denali National Park, she was once sitting in a nest with a young golden eagle in her lap when she noticed the incoming six-foot wingspan of an adult eagle carrying a ground squirrel. The eagle saw McIntyre before it reached the nest, and dropped the ground squirrel before flapping to a cliff across the river.

"It was the neatest thing I've ever seen," she said.

McIntyre scrambled out of the nest and watched from afar as the adult eagle retrieved the ground squirrel and returned to the nest to feed its chick.

McIntyre has visited the nests of golden eagles in Denali National Park for the past 15 years, attaching identification bands to their legs and tiny transmitters to their backs to monitor their breeding success. Hers is the longest-running study of golden eagle ecology in the northern latitudes of North America.

Sometimes mistaken for immature bald eagles, golden eagles stand taller than two feet; the largest females weigh 13 pounds. In contrast to bald eagles, golden eagles have blond heads and dark tails.

Since 1987, McIntyre has migrated in spring to Denali Park from Fairbanks to study a sampling of the 100 breeding pairs of golden eagles that return each year to the park. Over the years, McIntyre has learned how to climb rock cliffs and to speak softly while dangling from a rope to calm young birds as she approaches.

For three summers, McIntyre attached tiny backpack transmitters to 48 golden eagles in July and early August. In the following months messages sent by satellite to McIntyre's computer showed her the locations of the birds. She worked with Mike Collopy, of the Environmental and Resource Sciences department at the University of Nevada Reno to determine migration routes, locate where young eagles spend the summer after they return north, and estimate how many young birds become adults.

From the three-year satellite telemetry experiment, McIntyre learned that Denali's first-year golden eagles leave their nesting territories from mid-September through early October after their parents abandon them. The young eagles in her study migrated as far south as northern Mexico; many of them wintered in the Rocky Mountains. Then, the young golden eagles flew north, but rarely back to Denali. They returned to other areas of Alaska; two wandered as far as the coastal villages of Wainwright and Point Lay.

Young golden eagles that migrate, like those born in Denali, face a rough road to adulthood. Biologists estimate that at least 75 percent of golden eagles, which can live to the age of 25, die before reaching sexual maturity at five years of age.

McIntyre said though the breeding birds are doing well in the protected wilds of Denali, she worries about their winter range in the Lower 48, northern Mexico, and Canada. One of the biggest threats is the invasion of cheatgrass, a species from Asia that is invading the Great Plains and the intermountain West, displacing native vegetation and reducing the numbers of blacktailed jackrabbits and other golden eagle prey.

"You can't name a western state that doesn't have a cheatgrass or invasive weed problem," said Collopy. "Sagebrush ecosystems throughout much of the west are becoming endangered."

Other threats to golden eagles include the encroachment of human development in such areas as San Diego Country and Colorado's Front Range.

"There's a lot of things happening (to golden eagle habitat) in the Lower 48," McIntyre said, "and they're all going on at the same time."