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It was an epic trip for a five year old. Shaa left from Chilkat Pass in southern Alaska, and traveled into the Yukon. He arced east toward the Northwest Territories, where he passed over the Peel River, turned southwest to the City of Dawson, crossed back into Alaska, turned around, crept along Kluane Lake, and finally settled in the Village of Haines Junction. And he did all this in just 10 days.
Shaa isn’t the son of a mountaineering explorer, sled dog racer, or floatplane pilot—he’s a bald eagle. In all, Shaa looped a 2,300-kilometer path over the Arctic—had he instead flown south in a straight line, he would have made it almost to San Francisco.
“He went on a soul-searching journey,” jokes Rachel Wheat, a postdoctoral researcher at the State University of New York.
Shaa was one of 28 bald eagles that Wheat and her colleagues caught and fitted with GPS transmitters. Using the satellite tags, the scientists tracked the birds’ movements from the spring of 2010 to early January 2016, watching from a computer as they zigzagged across southeastern Alaska and Western Canada. The study has important implications for the future of eagle conservation.
Bald eagles can journey great distances to follow salmon runs, but little is known about the details of their travels. Through their tracking study, Wheat and her team found that bald eagles have a number of different travel habits depending on their life stage and sex.
Shaa was just three years old when Wheat fitted him with a transmitter. The bird had been hunting on the Chilkat River in southeastern Alaska, one of the nearly 3,000 bald eagles that flock to the river flats each year to feed on a winter chum salmon run. Wheat later named him Shaa—“mountain” in the Tlingit language—because of how much time he spent in the Alaskan mountains.
Young male eagles like Shaa—those without the responsibilities of new parents—travel the most, venturing as far south as Vancouver Island in British Columbia, and as far north as the Peel River in Yukon.
But Wheat found that the habits of these traveling birds also differ. Some birds, which she calls migratory eagles, always fly the same routes. Nomadic birds, by contrast, are all over the place. Perhaps not surprisingly, nomadic eagles are all young—most are under age five.
“If you are a young eagle, you are probably going to be nomadic because you don’t know where to find food yet,” Wheat explains. She describes nomads as inexperienced birds that are exploring the landscape and learning where the good salmon runs are. “They don’t know what they are doing. They just bounce around like ping-pong balls.” She suspects that over time, those eagles will learn where the best salmon runs are, and will fly back to the same places year after year.
Then there are the eagles that are either parents or hopeful parents. Wheat calls them the breeders, and as her study shows, these eagles stay at home year-round to defend their nesting sites from potential competitors.
There’s one more category of eagles: localized birds, which do not go on long-distance travels.
The breeders and the localized eagles tussle the most for quality nesting sites. With an estimated growing population of 75,000 bald eagles in Alaska, there are more breeding-age birds than quality nesting sites, and competition for sites is fierce. Localized birds have the most trouble securing a nesting site. Their strategy is to wait: if a breeder dies or its nest is destroyed, a localized bird swoops in and takes its place.
Before Wheat’s research, scientists had a scarce understanding of bald eagles’ diverse travel ranges.
“You can’t paint protection of bald eagle habitat with a broad brush,” says Jim Watson, a research scientist with the Washington Department of Fish and Wildlife. “There is not a one-size-fits-all strategy for conservation,” adds Wheat.