Love Soars At Bernheim: First Breeding Pair Of Golden Eagles Tracked In U.S.
When traveling long distances, the first golden eagle pair tracked in the United States prefer to fly separately.
But we've known that for a while. What we now know, is that this pair, who winters at Bernheim Forest, is a breeding pair, which means scientists are no longer tracking friends. They have tracked, perhaps for the first time, a pair of golden eagles as they laid, hatched and raised their own young. And, yes, this news is coming to you on Valentine's Day.
Here's the backstory on this soaring romance.
Harper and Athena flew 1,700 miles across opposite sides of Lake Superior from Kentucky to their summer nesting grounds near the Hudson Bay in Manitoba, Canada.
The pair reunited on April 6, 2019, soaring together above Harper’s preferred nesting area. But the very next day, Harper flew off alone to spend the night on an exposed point overlooking the Hudson Bay. The frozen landscape spread before him. The temperature was negative 15. Above him, hung the possibility of a northern lights display.
“Why he would travel so far to spend one night on this frozen seaside location is a mystery, but we know he has made this pilgrimage to the Hudson Bay in each of the three years he was tracked,” wrote Andrew Berry, Bernheim Arboretum and Research Forest conservation director.
These are among the notes left in Harper and Athena’s GPS diaries. Berry spent several months sifting through data collected in 15-minute intervals by the GPS solar-powered trackers the golden eagles wear on their backs; all of which, Berry has recounted in detail on Bernheim's blog.
Berry synthesized the transmissions with information on weather, satellite imagery and golden eagle behavior, to paint a picture of a breeding pair as they nest, lay eggs and raise young.
Based on information from the Eastern Golden Eagle Working Group and others, Berry believes they could be the first breeding pair of golden eagles tracked in the United States, and possibly the world.
“To see them interacting together and to see what a full year looks like for a breeding pair,” Berry said. “I think it adds a lot to golden eagle conservation.”
The day after Harper’s solitary pilgrimage, on April 8, the pair selected the nest site, known as an eyrie. Berry wrote the nest appeared to be in the trees, a prime location among the “tundra, exposed rock and the boreal forest.”
Over the ensuing days, Athena made short trips, likely gathering materials to build not one, but two nests, as is common for golden eagles. But by April’s end, it appears Athena had settled on an eyrie. The female eagle spent much of the next six weeks at that nest.
Then on April 25, Athena left the nest, and for the first time Harper stayed behind. Berry notes this as the first big indication the pair were incubating an egg. It’s unclear how many eggs there were, but golden eagles ordinarily lay between one and three eggs, Berry said.
“And eventually she stopped leaving, and there was a period of about a few days where she didn’t leave the nest at all,” Berry said.
Beginning June 3, Athena sat on the nest for six days straight. Berry thinks this is when the egg(s) hatched. According to Berry, eaglets begin chirping as much as two days before they crack open their shells. They emerge with grayish, down plumage that turns white within a week, Berry wrote.
Based on Harper and Athena’s movements, Berry believes the pair spent the next several weeks raising at least one chick. Athena stayed on the nest, protecting the nestling from temperature extremes and predators. Meanwhile, Harper hunted and brought food for Athena to tear up and feed to the young.
By July, Athena began to take longer excursions from the nest. The young, now at least 25 days old, would have begun to grow the types of feathers that would allow them to take flight. What happened to the juvenile eagle(s) afterward is one of many mysteries still swirling around golden eagles.
“Little is known, very little is known. We know that they disperse and what they have told me is that the juveniles go their own way,” Berry said.
What is known, is that Athena and Harper are back in Kentucky at Bernheim Forest for at least another few weeks. They’ve stayed largely in the forested knobs, tucked back in the hollows because of the rain, he said. But when it gets sunny, they soar.
It's unknown if the pair's offspring returned to Kentucky with its parents, but this winter, researchers have seen multiple juvenile golden eagles in the same areas with Harper and Athena.
“We’ve even seen them interacting and seen one of our golden eagles that’s tracked in a tree with a juvenile golden eagle,” Berry said.
Even with all that data, there remain so many unknowns about golden eagles.
“How did Harper and Athena form a pair? Did that happen in Canada or Bernheim? And if it happened in Bernheim in the winter, how did they migrate separately back to the same place in Canada?” Berry asked.
Berry said the data shows just how incredible these migratory apex predators are, and how much there is left to learn. But the only way that will happen, he said, is if people prioritize the conservation of large forested areas the eagles need to survive.
“We’ve got to act now if we’re going to keep these around,” Berry said. “Because if we can’t keep the large forest blocks around then we’re going to lose a lot of these incredible migratory birds like the warblers, but also species like the golden eagles.”
Eagle week at Bernheim Forest runs from Feb 17-21 and will feature a number of eagle-themed events, culminating in a lecture given by Berry on Friday Feb. 21 from 12 to 1:30 p.m.