VOYAGEURS NATL PARK — The numbers tell a devastating story that went largely unnoticed outside the scientific community. In Michigan alone, bald eagles lost over 400 breeding pairs to avian influenza — a staggering 40 percent decline that has shaken researchers who spent decades watching the species recover from near extinction.
“If you asked anybody in Michigan how the eagle populations are doing when we have over 600 pair, they say, great. We see eagles all the time,” said Dr. Bill Bowerman, a wildlife researcher from the University of Maryland. “So if we weren’t out there studying the population for the remediation of the Great Lakes contaminated sites, we would have missed it.”
At Voyageurs National Park, the impact was even more severe. Bowerman estimates that two-thirds of breeding pairs disappeared due to bird flu. “Last year at this time … we had no nestlings,” he said. “We should have had eight to 10 birds.”
A mission despite lost funding
That’s why Bowerman showed up at Voyageurs again this year — even after his federal research funding was cut. What was officially a scientific field expedition to band bald eagle nestlings felt more like an urgent rescue mission, a gathering of the “Voyageurs National Park Eagle Lovers Club” determined to document whether the species could bounce back.
“The future looks brighter,” Bowerman said after this year’s banding effort. “It’s been pretty grim in terms of looking at what we’re seeing in our monitoring results. I don’t think we’re where we were five years ago, but we’re much better than we were last year. That’s good.”

The hidden collapse
For decades, the story of bald eagles in the Midwest had been one of steady, even spectacular recovery — until 2022, when avian influenza began hitting the region’s raptors hard. The real impact didn’t become clear until researchers began comparing 2023 survey data.
“The bird flu epidemic was occurring within the 2022 breeding season,” Bowerman explained. “So you couldn’t look at the number of nests that it was affecting, because you could have one adult survive, one die, you know, and it was ongoing. So, really, you had to look at the 2023 data.”
What made the collapse even more alarming was the absence of natural recovery. Typically, when breeding territories open up, non-breeding adults called “floaters” move in to fill the gaps.
“We didn’t see that,” Bowerman said. “So the non-breeders were affected also.”
Up in the canopy
Getting to the truth meant going up — sometimes way up. Supported by wildlife staff from Voyageurs and seasoned volunteers, the team spent a weekend visiting nest sites scattered across Namakan, Sand Point, Kabetogama and Rainy lakes, with massive eagle nests perched anywhere from 40 to 90 feet above ground.
Mike Wierda, an associate professor with the Utah State University Extension Service, served as the team’s designated climber. In a touching nod to former longtime climber and team member Terry Grubb, much of the gear Wierda used had belonged to Grubb.
Wierda’s job was to ascend to the nest, gently collect the eaglets, place them into a soft bag and lower them down to the ground crew waiting below.
“This is the first time a human’s been in their nest,” Bowerman reflected on the intensity of the moment for both the climber and the birds. “It’s a really unique experience.”
Once an eaglet was lowered to the ground crew, Julia Ponder, former director of the University of Minnesota’s Raptor Center, weighed it — most came in between three and five kilograms. She then examined each bird on a picnic tablecloth while team members held the eaglet’s legs and covered its head with a hat as she drew blood samples.
Two vials were filled: one for testing metals like cadmium, lead and mercury; the other for contaminants such as DDT, PCBs and PFAs. Bowerman personally delivered the samples to the U.S. Fish and Wildlife Service lab in East Lansing, Michigan, for analysis.

Signs of hope
By Saturday, the team had banded 10 eaglets and were optimistic, though Sunday’s high winds and rough water prevented further work. “Unfortunately, we didn’t get any other birds banded on Sunday because we encountered unsafe high wind and waves and the eaglets we observed were too old for Mike to attempt wrestling into his bag,” said wildlife technician Jake Schiefelbein.
Still, the contrast with the previous year was striking. The team banded three eaglets on Friday alone — a marked improvement over the same period when they found no nestlings at all.
The irreplaceable datasetVoyageurs has played a unique role in eagle research since 1989, serving as what Bowerman calls the “out-of-Great Lakes Basin control site.” The park now houses one of the longest-running datasets on bald eagle populations anywhere — a resource that has become increasingly rare as other monitoring programs ended due to successful recovery.
“Some of the standbys like Sweden had comparable data to Michigan,” Bowerman said. “And then the last few years, they’ve got very little data because they recovered.”
Lee Grim, a former park biologist who began monitoring eagle nests in the park in 1973, said more than 370 sites have been tracked over the decades. Each year’s banding work requires weeks of preparation, typically beginning in April — though this year the lakes were iced in until May 10.
“It takes a whole host of people to do it,” Grim said. “It takes an administration to say, yeah, we need to do this, we approve that, here’s some funding for it. It takes Bill to say, yeah, we want to come. It takes Jake and Abby, the people in resource management, to keep the records and all that kind of good stuff and do the reports and keep it all going.”

The larger stakes
Bowerman often encouraged the team to take advantage of the “200 combined years of eagle experience” available to them — expertise that becomes more valuable as monitoring programs elsewhere disappear.
Without year-over-year data, he noted, population shifts can go unnoticed behind occasional flyover sightings. At Voyageurs, that kind of long-term monitoring is the only way to see what’s really happening in the treetops.
“If you don’t have a national park that has the public interest and the concern and the ability to maintain those long-term datasets, we’re not going to be able to tell these stories,” Bowerman said.
And while federal research funding has become less reliable, the value of parks like Voyageurs extends beyond data.
“These national parks, they’re the last places that we can really have an understanding of how to protect our natural world.”