The number of golden eagles that spend summers in Alaska is more than three times the previous estimate, biologists have just determined.
At least 12,700 of the 12-pound predatory birds migrate to Alaska each summer to create new golden eagles. This number represents about a quarter of all golden eagles in North America.
Several scientists from Alaska and one from HawkWatch International in Utah calculated that the new estimate improved over an old one (around 4,000 birds) that scientists thought was too low. This was especially the case after biologists Carol McIntyre and Steve Lewis in 2014 counted more than 1,300 migrating golden eagles from a single location over nine days of observation in the Mentasta Mountains.
The authors of the December 2021 article, Golden Eagle Abundance in Alaska, are not saying that there is a recent golden eagle boom in Alaska. The new number, reported in the Journal of Raptor Research, is what they think is a more accurate estimate.
Travis Booms is a biologist with the Alaska Department of Fisheries and Game in Fairbanks who helped design and execute the study, based in south-central Alaska. Knowing roughly how many animals there are helps managers know if this creature is doing well or in need of special protection.
Chocolate brown golden eagles are roughly the same size as bald eagles. Instead of congregating around rivers like bald eagles, goldens prefer open countries with mountainous slopes and tundra landscapes.
There, the birds use curved talons the length of human fingers to pierce their prey, which includes ground squirrels, ptarmigan, snowshoe hares, and sometimes even caribou and muskox calves.
To better count the golden eagles visiting Alaska in the summer, Booms and his colleagues chose to watch birds fly in a corridor between the Chugach and Talkeetna mountains.
A good place to settle was near Gunsight Mountain, halfway between Palmer and Glennallen. There, for a few weeks from mid-March 2014 to 2018, biologists and technicians counted golden eagles returning north from their wintering grounds.
They also captured the birds by depositing road-killed carcasses that could not be recovered, then firing a gun that threw a net at hungry migrating eagles that alighted on the bait.
Once they caught an eagle, the biologists rushed in and cut the net. They then placed a leather hood over the eagle’s head, which somehow calmed him down.
They also placed a pair of leather slippers on the bird’s paws.
âThese talons can go through your forearm,â Booms said, noting that golden eagles, unlike bald eagles, rarely strike with their beaks.
During these four spring seasons, biologists outfitted 53 birds with backpack transmitters about half the size of a deck of cards.
Then came what Booms considers one of the most memorable moments of his career. He or some other biologist tossed the giant bird into the air and felt the breath of air coming from wings as wide as their open arms.
The transmitters – six of which are still in operation this month – have allowed biologists to determine that golden eagles that migrate along the Glenn Highway spend summers in the mountains around Anchorage in central and western the Alaska Range, and as far west as the Kilbuck Mountains near Bethel. Currently, in early December, most of the birds have returned to the western United States, Canada and Mexico.
Biologists extrapolated figures from the Gunsight Mountain group they studied to come up with Alaska’s new estimate of the majestic bird that rests on the state’s vast open spaces.