I had been sitting in the observation blind for a couple of hours when I heard a commotion outside. Looking through the one-way glass, I saw an enormous bird with a golden crown and talons that were built for serious damage. Another landed nearby. I knew immediately that they were golden eagles, which are one of the largest predatory birds in North America.
These majestic birds, common in the American northwest, migrate long distances in the fall and spring between their summer and winter ranges. The distances they cover can vary depending on where the eagles start, but they generally follow the same routes back and forth. Those that travel the farthest are the golden eagles of Denali National Park.
Immature goldens spend the summer forage around Denali while the adults mate and nest there. Golden eagles generally reach maturity at four or five years. Eaglets hatch near the end of May or early June, and after they’re just two months old, the chicks begin to learn how to fly. During the next eight weeks, they rely on their parents for food and protection, but at about four months of age, in late September or early October, the eaglets leave the nesting areas and begin the migration south. Adults follow a few weeks later.
This fall migration often takes the birds through western and southwestern Montana. Large numbers of solo eagles tend to migrate along the Rocky Mountain Front toward wintering grounds in the lower 48 states.
Along the way, the prairies abutting the foothills offer these birds of prey prime foraging habitat for a meal of black-tailed prairie dogs, Columbian ground squirrels, migrating waterfowl, and even young raptors of other species.
The updrafts along the mountains also provide a boost for the eagles, allowing them to fly farther without tiring as quickly.
Denali’s golden eagles have been observed wintering in Kansas, Colorado, Texas, New Mexico, and even northern Mexico. They remain in their wintering grounds for a few months, sometimes moving even farther south before returning to Denali in late March or early April.
Rob Demenech, of Missoula’s Raptor View Research Institute, has surveyed and tracked fall migrating golden eagles along the Rocky Mountain Front for more than nine years. During the 2007 migration, he and his helpers observed 396 golden eagles passing through the study areas near Rogers Pass and the Bridger Mountains in September, most of them immature goldens. In October they recorded 1,902 eagles, mostly adults. In 2008, one eagle was tracked over its entire migration south of Montana. It stopped in Colorado for some time before continuing to the southern tip of Texas. Golden eagles can migrate more than 3,000 miles; this bird flew over 3,100 miles one-way.
If you recognize a golden eagle overhead, think about where it came from. It might be enroute from central Alaska all the way to Mexico, passing like clockwork over our state each fall and spring.
"Field Notes" is produced by the Montana Natural History Center.