Every day from August through October, researchers, volunteers and visitors gather atop Cadillac Mountain to count hawks, falcons and eagles migrating over Acadia National Park, data scientists rely on to gauge how climate change is reshaping the region’s ecosystem.
The multi-month count comes as key tenets of the landmark Endangered Species Act have been dismantled under President Donald Trump’s administration, allowing for the inadvertent killing of imperiled species. The act protected two of the most iconic birds that inhabit Acadia — bald eagles and peregrine falcons.
The administration’s new interpretation of the environmental law compounds growing concern around climate change impacts on endangered species.
More than 200 sites in North America participate in Hawk Watch, an initiative spearheaded by the Hawk Migration Association to track raptors during their fall exodus. Since 1995, when researchers first brought the count to Mount Desert Island, they’ve tallied more than 71,000 raptors soaring above the mountains of Acadia.
Still, not all spotting days are successful — and researchers would like to know why.
“We have great migration days weather wise, but we don’t have a whole lot of birds and we don’t know why,” lead counter Angi King Johnston said Wednesday morning on Cadillac Mountain’s summit. “To understand why, the first thing you have to do is document, and that’s why this research is so incredibly important.”
The Hawk Watch is led by park officials in partnership with the Schoodic Institute, a nonprofit research hub, and Friends of Acadia, a local conservation group. Throughout the past three decades, the park’s counting team has had to adapt to new migratory patterns largely caused by climate change.
They now track turkey vultures — which weren’t of concern until 2004, when the large birds began moving northward — and they’ve started counting in August, as some raptors are now migrating earlier in the year, Johnston said.
In the early 1970s, the United States banned DDT, a pesticide used to control insect infestations that had devastating effects on many birds of prey species, including bald eagles and peregrine falcons, according to the Peregrine Fund, a nonprofit conservation group. Since then, with the adoption of the Endangered Species Act, some once at-risk raptor populations have recovered.
Along with peregrine falcons, bald eagle populations have rebounded and were removed from the endangered species list in 2007.
“It’s very important that we keep the count going so that we can understand how those changes are affecting raptor populations,” Johnston said. “They are also great bioindicators as to how healthy an environment is. We knew that things were not good in the mid-1900s, with the use of DDT, so we know that by keeping track, there are early signs that something is not quite right.”
But there’s still much unknown about how climate change is impacting raptors. In mid-September, the group had its busiest day this season with 573 birds spotted. Yet Johnston wonders if the season’s count will end below the region’s 30-year average, in part because birds of prey have struggled to raise their young due to shifting environmental factors.
The raptor count is largely facilitated by park visitors who join the spotters stationed off Cadillac North Ridge Trail. Roughly 3,500 visitors take part in the count each year, Johnston said, adding that some come specifically for the event while others inadvertently stumble upon the group on their descent or ascent up Acadia’s tallest mountain.
Within two hours Wednesday morning, John and Lisa Winebrenner, a couple visiting from Indiana, spotted roughly six birds over the skies of Frenchman Bay.
The pair, who travel for bird watching, usually join an annual hawk watch in Ontario, Canada. This year, on a road trip throughout New England, the couple stopped for one day in Acadia to spend their morning spotting migrating raptors.
“It varies: you have a slow hour and then you’ll have an hour of a whole bunch, so you never know,” John Winebrenner said. “That’s what draws me — you never know what you’re going to see.”