An Eagle Eye to the Sky

by Gabrielle Balzell

Volunteers gear up to brave the cold in search of these magnificent birds.

The national emblem of the United States since 1782 and a sacred symbol in Native American culture for centuries longer, the bald eagle (Haliaeetus leucocephalus) is among nature’s most majestic creatures. Each winter, they can be spotted soaring high above the treetops dotting the shorelines of the Illinois River, drawing birding enthusiasts and curious onlookers alike out into the cold for a glimpse. But not too long ago, the bald eagle’s presence along Midwestern waterways was uncommon—and its very existence threatened—as the species struggled to overcome habitat destruction, illegal hunting and the contamination of its food source.

The Ultimate Comeback
“It’s a great example of how the Endangered Species Act… and everything can come together to bring a species back from the brink of extinction,” declares Mike Miller, president of the Peoria Audubon Society, a birder for more than two decades, and coordinator of the Peoria Eagle Count. Now in its 53rd year, the Peoria Eagle Count is a census of the bald eagle population along the Illinois River from Henry to Havana conducted every January—and part of the Eagle Nature Foundation’s (ENF) larger Midwinter Bald Eagle Count, which tracks the birds’ numbers along waterways from Minnesota to Louisiana.

While the bald eagle was removed from the U.S. Fish & Wildlife Service’s “endangered” species list in 1995 and its “threatened” species list in 2007, the counts act as a valuable checkup on the birds and their habitats. “One of the reasons we’re interested in eagles is as an indicator,” Miller explains. “They’re what we call an apex predator; that means they’re at the top of the food chain… If the apex predators are healthy and reproducing, that tends to indicate you have a healthy base supporting their population. When their population crashes, that tells you there’s definitely something wrong.

“It’s kind of the canary in the coal mine,” he adds. “Because we live in the same system the birds do, it’s a good indicator of the ecological health where we live. And what affects them does affect us.”

The damaging effects of DDT, for example, were first observed in bald eagles and other predator birds in the 1960s, when researchers discovered the insecticide was affecting their calcium metabolism and reproduction, causing eggshell-thinning and even sterilization—a primary factor in the species’ U.S. population plummeting to just 487 nesting pairs in 1963.

“We’d been using a chemical in the environment that was accumulating in the tissues of birds,” Miller notes. “Well, that same chemical was also accumulating in our tissues. We don’t lay eggs, so we weren’t seeing immediate evidence of what it was doing to us. But you know it can’t be good for you to have this calcium-depleting agent running rampant through the population.”

The Environmental Protection Agency took notice of these noxious effects, and in the years since the passage of a federal ban on DDT in 1972, the bald eagle has experienced a remarkable rebound. Last year, volunteers spotted just over 3,900 eagles during the daylong Midwestern count. In June 2007, the U.S. Fish & Wildlife Service reported approximately 9,790 nesting pairs of bald eagles in the United States, indicating a national population that likely totals well over 19,500. While impossible to pinpoint a precise number, the ENF estimates between 35,000 and 50,000 exist in North America today.

Counting on Volunteers
While federal agencies employ only seasoned researchers and analysts to determine their estimates, programs like the Peoria Eagle Count can utilize the observations of volunteers. “It’s what we call citizen science,” Miller explains. “It’s an opportunity for the non-professional to make a contribution to collect scientific data and information.”

For the Peoria team, it starts with the deployment of five teams, four on shore and one on water. Count Day begins with the shore teams positioning themselves along either side of the Illinois River, two in Henry and two in Peoria, while the boat team floats out to the main river channel at Pekin. From there, the teams travel south along their assigned routes, stopping at predetermined observation points where they search the sky and tree lines for the birds’ telltale markings.

At each stop, volunteers record their location, time of observation and number of sightings, taking care to note the approximate age of each bird. “It’s important to know the ratio between adults, sub-adults and immatures,” Miller remarks. “If every bird you see out there is an adult, then you know something’s going on with reproduction; you’re not getting new birds into the population.”

Once the volunteers have covered the 80-mile route, the teams regroup to compare their findings, eliminating any duplicate sightings, before sending the information to the Eagle Nature Foundation to be incorporated into the larger Illinois and Mississippi River counts.

Under Our Wing
Last year, Miller’s team spotted just short of 350 bald eagles, a relatively high number for central Illinois. “A typical year, we’re probably looking at 250 to 300 birds… on our count—and those are just birds we’re able to observe,” he says. “There are undoubtedly more that we can’t see.”

But the count is just “a snapshot of a winter,” he adds. “[They] will vary greatly from one year to the next, depending on the water and conditions north of here.”

Though Illinois has its fair share of resident bald eagles—Miller estimates up to 300 nesting pairs—the vast majority sighted in the January count are migrating south in search of open water and available food. “Eagles are not necessarily what we would consider a… long-range migrant; they’re kind of an opportunistic migrant. They will only migrate as far as they need to stay with open water,” he explains. “The reason they’re here is because everything is frozen up north: Wisconsin, Minnesota, southern Canada. When those areas are socked in with ice, all the birds are down here. But… those birds won’t necessarily come down here in mild winters.”

During particularly harsh northern winters, flocks of bald eagles can often be found scavenging the shores of the Illinois River up until early spring. It’s a spectacular sight that Miller and other birders hope to see for years to come. “When I first started doing this, there were no eagles nesting in any of these counties,” he recalls. “Since that time, they’re nesting all up and down the river, and not only on the Illinois River; we’re seeing them starting to nest in tributaries.”

Yet Miller worries the bald eagle’s grand comeback could be reversed if the demand for increased grain and corn production results in an additional loss of bottom-land habitat to farmland, while other conservationists are concerned that pesticides are once again working their way into our waterways and up the food chain. Regardless, Miller believes it is society’s obligation to preserve this enchanting, emblematic creature. “It is our national symbol,” he asserts. “We have a responsibility to do that.” a&s

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