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Bald Eagle Renaissance

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For twenty-five years, OSU researchers have documented the return of bald eagles to Oregon.

We were in an airplane looking for bald eagle nests up off the north fork of the Umpqua River. We must’ve hit some kind of down draft,” recalls wildlife biologist Bob Anthony. “The next thing I knew, we were heading down through the trees. When I woke up I was hanging upside down from my seat belt.”

“After the fixed wing incident we switched to helicopters. Helicopters are easier to maneuver in rugged country and between treetops,” explains Frank Isaacs, another OSU wildlife biologist. But then there was that winter survey on the Grande Ronde in northeastern Oregon.

Looking out onto a forest from the inside of a helicopter.

Frank Isaacs logs 50 hours in a helicopter every year, searching for active eagle nests. Photo: Lynn Ketchum

“We were almost done—heading up the Wallowa,” remembers Isaacs. “I was looking down at the river trying to count eagles. I heard the pilot yell something. When I looked up, a power line was right in front of us. The pilot turned the helicopter on its side… so the rotor came down and cut the power line. It broke the plastic bubble at our feet and damaged the cowling around the rotors. But we didn’t get tangled in it, and he was able to land the helicopter. That’s why the first thing we look for are power lines, then we look for eagles.”

If Anthony and Isaacs have learned anything during the past 25 years, it’s that studying bald eagles is an adventure. Bob Anthony is the leader of the Oregon Cooperative Fish and Wildlife Research Unit at OSU’s Department of Fisheries and Wildlife. Frank Isaacs is a senior faculty research assistant in the department.

After 25 years of continuous monitoring in Oregon and along the lower Columbia of Washington, the two researchers have developed a clear picture of the life and times of Oregon’s bald eagles. That picture is a good one for our national symbol. Populations are on the rise and have been since the researchers began their study.

Before you can study bald eagles you have to find them. From the beginning of their project, the two researchers relied on aircraft to search for occupied nests. They also used a lot of shoe leather and rubber—hiking and driving all over Oregon. Often it took both air and ground reconnaissance to pinpoint a bald eagle nest and confirm evidence of nesting success.

Once they confirmed an active nest, the researchers made a house call. During the early years, they climbed to the tops of tall trees to examine young eagles at close range. Knowing that an adult eagle could land a solid punch or slice a scalp, Anthony, Isaacs, and graduate student Richard Frenzel were cautious as they counted eggs, banded chicks, collected prey remains, and extracted blood samples from the nestling eagles.

Bearded man looking through a scope near a tree-lined highway. Bearded man leaning out of the window of a van, which is loaded with camping gear. A dog is sitting outside the van.

Increasingly, Isaacs finds eagles nesting close to human activity, such as along this busy road, as well as in remote wilderness areas. Photo: Lynn Ketchum

OSU wildlife biologist Frank Isaacs has tracked bald eagles by land, sea, and air, for years accompanied by his faithful companion, Tule. Photo: Lynn Ketchum

When the researchers began their first field season in the spring of 1978, they had a long “to-do list.” Count how many bald eagles are in Oregon and the lower Columbia. Study the effects of contaminants. Map the distribution of their nests. Determine their habitat preferences. And monitor their comings and goings.

At that time, the symbol of the nation was on the endangered species list, and the researchers’ work was aimed at helping landowners and agencies do a better job of managing for the species.

In 1978, the researchers found only 57 breeding pairs of eagles in Oregon and along the lower Columbia in Washington. In 2003, they sighted 458 nesting pairs in the same area. In the 1970s, there were no nesting pairs on the Willamette River; today, up to 25 pairs make the Willamette area their home at least part of the year. Just like returning eagles, the pair of researchers have come back year after year to check on them.

“Early on, I thought I would be documenting the demise of the eagles; instead I saw a recovery,” Frank Isaacs says. “Now eagles are so widespread in the state it’s hard to be somewhere in Oregon and not be in bald eagle territory.”

Isaacs should know. As the lead field observer, he logs more than 50 hours in helicopters every year checking nests, and drives more than 10,000 miles to monitor some 498 territories. (A territory represents the potential for a nesting pair of eagles.) Over the years, Isaacs has used bicycles, canoes, snowmobiles, and cross-country skis to get a glimpse of nesting eagles. And he’s worn out two Volkswagen buses bumping along Oregon’s back roads documenting the eagle’s comeback.

“My favorite part of this whole thing is exploring. It’s like a treasure hunt—looking for nest trees,” Isaacs says. “It’s a great game. You get clues. People send in reports. You go to the place…find the eagle…find the nest … determine the status of the nest.” And the researchers try to do it all without disturbing birds. “We don’t want to negatively impact their nesting success,” Isaacs adds.

The result is a generation of data documenting the number of adult eagles, the location and distribution of nests, chick counts, and habitat preferences.

Mother and baby eagle in a nest. Two juvenile bald eagles in a nest.

A bald eagle nest. Photo: Pat and Tom Leeson

Two juvenile bald eagles attest to a successful nest and the comeback of eagles to Oregon. Photo: Frank Isaacs

“It’s one of the best and most consistently collected data sets on eagles in the country because of Frank’s dedication, thoroughness, and keen sense of observation,” project leader Anthony says.

The roots of the landmark study go back to the early 1970s, when bald eagles were first listed as an endangered species and a logger named Bob “Cupie” Ziak worked the woods near Astoria.

“He loved bald eagles,” Isaacs says. Cupie’s fascination with the birds, and his concern over their future, pitted him against the paper company Crown Zellerbach.

“He blew the whistle on Crown Zellerbach in the mid-1970s,” Anthony says. Cupie’s complaint came after the paper company logged an area near Astoria, leaving a bald eagle nest tree standing alone in a clear cut. When the U.S. Fish and Wildlife Service threatened to sue the company for violating the Bald and Golden Eagle Protection Act, the paper company settled out of court, agreeing to fund a two-year survey of bald eagle nests. That was 1978.

Anthony was studying small mammals at OSU when the Oregon Cooperative Fish and Wildlife Research Unit leader asked if he wanted to work on bald eagles with the research funds from Crown Zellerbach.

“I said, ‘Well, sure. It’s a pretty glamorous species…one that people care about.’ And that’s how it all started,” says Anthony.

Over the years, the eagle research team has included several graduate students and research assistants, but it’s Frank Isaacs who’s been in the field since almost the beginning. Anthony hired Isaacs after the first year. With degrees in forestry and forest wildlife management, Isaacs knew about the trees and forests that bald eagles prefer for nesting and roosting. But he didn’t know much about eagles.

Bearded man holding binoculars. Clouds and forest are behind him. Close-up of a juvenile bald eagle.

Project leader Bob Anthony has witnessed the return of bald eagles to the Willamette River. Photo: Lynn Ketchum

A juvenile bald eagle. Photo: Frank Isaacs

“I’d seen a couple and that’s about it,” Isaacs says. “Cupie ‘took me under his wing’ and helped me learn about eagles on the lower Columbia.” Soon, Isaacs found other mentors, including Ralph Opp, a state wildlife biologist in Klamath Falls, and Bob Anderson, a biologist for Weyerhaeuser. It wasn’t long before Isaacs was smitten. He quickly learned that bald eagles are masters of the air.

“They deal with air like a fish deals with water,” Isaacs says. “They can read it. They can feel it…probably even see it—they somehow know what air to take advantage of and what to avoid.”

It was supposed to be a one-year field research gig for Isaacs. But with additional funding from U.S. Forest Service, Bureau of Land Management, Oregon Department of Fish and Wildlife, U.S. Fish and Wildlife Service, U.S. Geological Survey, Weyerhaeuser Company, and many other groups, the one-year hitch has turned into a 25-year career. In that time, both biologists have seen dramatic changes in bald eagle populations and learned plenty about the creature’s habits.

The scientists believe as many as 1,000 pairs lived in the region in the days before Euro-American settlement. But routine shooting, trapping, and poisoning decimated the bald eagle population until the mid-1930s. With increased pesticide use following World War II, reproduction declined from those surviving eagles. According to Isaacs, it wasn’t until after DDT was banned in 1972, and the bald eagle was added to the endangered species list in 1978, that the population started recovering.

By the mid-1980s, the number of nesting pairs had almost tripled. With growing numbers of eagles across the state, the biologists needed help keeping tabs. In the spirit of Cupie Ziak, they turned to volunteers for help.

“Every year you’d run into somebody else like Cupie,” Isaacs says, “people who just love eagles.”

Arnie Ambuehl is one of them. He had no particular interest in birds until a pair of bald eagles moved in near his Lake Oswego home. The majestic birds caught the eye of the retired sheet metal worker. “They’re kind of unique. How many neighborhoods have eagles at the end of the street?” Ambuehl says.

He didn’t just watch them. Ambuehl photographed and videotaped the eagle pair from the time they showed up in late winter until their fledglings took their first flight. He even cut a window into the end of his house for a better vantage point to view his seasonal neighbors.

Eaglet in a nest. Man looking through binoculars at nesting eagles.

During the early years, researchers scaled to the tops of tall trees to band and weigh young eagles in their nests. Photo: Frank isaacs

Frank Isaacs spots a nest near Crane Prairie Reservoir in central Oregon. Photo: Lynn Ketchum

Bill Price, a retired Tualatin fireman, is another eagle fan. He’s been on the survey since 1995 and now helps coordinate an army of some 300 volunteers. All in all, nearly 1,000 people have contributed to the project, from bird watchers who report a single sighting to long-time volunteers who have documented the eagle’s revival. Looking back over 25 years at the steady increase in population—which has doubled every ten years—Isaacs has developed a theory about Oregon’s eagle recovery.

“Eagles were persecuted for generations by people and as a result the birds lived in more secluded places and avoided people.” Then DDT was banned, protective laws were passed, and people learned more about the birds.

“I think people have changed,” Isaacs says. With less harassment, eagles have moved into habitats closer to people.

From the Portland suburbs in Lake Oswego to an industrial development in Sweet Home, bald eagles know how to survive in a variety of situations. The researchers found that now bald eagles nest where they can find food in good supply and trees for nesting and perching, even if it’s around people.

Bald eagles, Isaacs thinks, are intellectuals. “I think they live less on instinct and more on knowledge,” Isaacs says. They have to learn their place. Eagles nesting on Ross Island near downtown Portland have to live differently than eagles nesting in the wilderness near Crater Lake. “They adapt to different situations.”

Mother eagle feeding baby eagle in a nest.

Survey volunteer Arnie Ambuehl built a new window in his Lake Oswego home to observe this eagle family—and photograph their success. Photo: Arnie Ambuehl

Years of research have produced new knowledge about eagles, including their reputation as scavengers. Anthony believes that reputation may be undeserved, at least among adults in breeding territories. “They are extremely efficient predators. They will take just about any kind of fish, bird, or mammal. The diversity of the diet and the efficiency with which they take prey is intriguing,” says Anthony.

Despite 25 years of fieldwork that’s produced volumes of data on the productivity, locations, and movement of Oregon’s bald eagles, there still are questions. For example, scientists know that some West Coast eagles travel north to British Columbia in late summer, that birds from the northern interior of Canada come south to Oregon in winter, and that some southwest eagles come north in the fall. But researchers don’t know much about what happens to young Oregon eagles after they fledge from the nest.

Anthony and Isaacs hope to use satellite telemetry to help solve that mystery. Attaching transmitters to chicks and tracking them with satellites would help scientists pinpoint migration corridors and reveal “where in the heck they go and what they do over several years time,” Isaacs says.

Cupie Ziak missed the silver anniversary of the OSU eagle survey. He died in 1990. But his legacy can be found in what’s become one of the most comprehensive and long-running bald eagle surveys in America. Now with 25 years of data behind them and plans for even more study, Anthony and Isaacs are helping the rest of us understand the bald eagle. But more importantly, by documenting the ways of the bald eagle, the team has helped landowners and agencies make management decisions that will help ensure the future of America’s symbol in Oregon.

Published in: Ecosystems