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Voyageurs National Park, Minn. — In Voyageurs National Park, if you're looking, it's hard to miss the bald eagles.
The majestic birds glide overhead, or silently perch on a protruding waterfront branch. Adults are distinctive. They weight a good 10 pounds, with iconic white head and tail feathers. Their branchy nests fill the top of white pine trees -- sometimes 10 feet across.
Thirty years ago you might have been hard pressed to spot America's national symbol. As recently as the 1980s, it was obvious that eagles were still struggling, according to park biologist Lee Grim, who has been monitoring eagles since 1973.
"We saw how some of these birds were ill, and sick, and they had avian pox and things," Grim says. "Something was keeping them from being healthy."
Voyageurs Park holds a dubious eagle record.
"In 1989 we found a bald eagle, just down the lake here, about four miles, that had the highest known concentrations of some of these contaminants that were ever recorded in the literature in North America," Grim says. "We wanted to know why is that up here in northern Minnesota, in the middle of a beautiful, almost wilderness area."
Researchers began studying the toxins around Voyageurs, and where they might be coming from.
To understand eagles, it helps if you can get very close. That's why U.S. Forest Service naturalist Teryl Grubb is inching his way up the branches of a 90-foot tall white pine tree to check on an eagle nest. A pair of eagles circle overhead. They won't attack, but they're clearly upset. Grubb crawls over the nest's edge, and pauses for a little chat.
He speaks softly to a pair of hatchlings -- fuzzy, beaky, and surprisingly big eight-week-old bald eagles.
Soon, one's headed to the ground, squirming in an orange bag, tethered by a long rope -- and right into the hands of graduate students Faith Wiley and Katie Parmentier.
They open the bag tentatively and squeal at the eaglet, who's trying with little success to look menacing.
A few minutes later, the bird is heading back up -- short a few feathers for mercury testing, and a little blood for other chemical tests. She has bright yellow feet with shiny black and very dangerous talons -- and a new pair of metal bands riveted around her ankles.
It's believed there were once half a million bald eagles in North America. As people spread, eagle numbers plummeted. Their last refuges in the lower 48 states included Maine, Florida, the Pacific Northwest, and the Great Lakes Region. There were so few bald eagles by the 1940s, Congress passed special protections, decades before endangered species was even a term.
But the eagles weren't coming back through the 1950s, the '60s or even the '70s. Now we know why. The insecticide DDT makes bird eggs fragile, and thus more likely to break under a 10-pound eagle than hatch. Biologist Lee Grim says DDT was sprayed all over the place.
"DDT is pretty much everywhere," Grim says. "It has been, you know. It wasn't too long ago that the Forest Service in places was spraying DDT for spruce budworm and other forest insects that were in the forest areas," Grim says. "That was around in this area ... and we have records of that back into the '50s."
Grim says "It's a pretty long-lived chemical."
Eagles are considered a sentinel species. They'll eat seagulls, loons, and pelicans, and lots of fish like northern pike. Essentially, they ingest whatever their prey has eaten. Toxins have an immeasurable effect on the smallest creatures. But eat enough of those creatures, and the toxins build up. We saw it in the eagles, through misformed beaks and fragile egg shells, and birds that were just not well.
Now DDT is banned. So are PCBs, chemicals which are known to cause cancer. Lee Grim says you can still find the chemical's traces, but not like it used to be.
"And the good news is that they're going down," Grim says. "And you don't find that out unless you look."
So we know what's been hurting eagles, although it's still something of a mystery how industrial chemicals like PCBs get up here.
Bill Bowerman, an environmental toxicologist, has been monitoring chemicals in Voyageurs' eagles for 15 years. Bowerman says bald eagles endured more than toxic pollutants -- they were abused. It took decades to get people to stop shooting eagles, and to avoid accidentally catching the birds, say, when trapping beaver.
"The eagle was protected. People learned more about them," Bowerman says. "And it's evident, when I go out to landowners that have eagle nests on their property, that they know how to manage their eagles -- how to keep people away, and how to protect that eagle during that critical nesting period."
In Voyageurs, bald eagle numbers have jumped from seven nesting pairs in 1973, to 28 breeding pairs today - 55 nests overall. There are more than 7,000 nesting pairs nationwide. That's enough to take the birds off the endangered species list.
But there are always new threats. Bowerman says the biggest may be from new diseases, like West Nile virus.
"One of the first birds that died after West Nile was discovered in New York City were the eagles, in the zoos," Bowerman says. "So, we have a worry about West Nile virus. And we have several pairs that just seem to be gone in Michigan when we were looking for them."
And there are new chemicals to worry about, like poly-brominated flame retardants. Their effects are unknown, but traces of them are doubling in the Great Lakes basin every three to five years.
Bowerman worries that government might ease up on the chemical industry, letting new and poorly understood toxic chemicals into the market, and the environment.
"As long as we maintain our vigilance about the environmental toxicants that are being created each year, and we maintain the strong environmental laws that we have for listing these different chemicals, and not allow them to go out on the market too quickly -- before we know what their potential environmental effects are -- we should be having the eagles protected," says Bowerman.
The American bald eagle is on track to be removed from the nation's list of threatened and endangered species. The action was first proposed during the Clinton administration. An official announcement is expected this summer, followed by a 60-day public comment period. Delisting could be official by the end of the year.