APPLE RIVER, Ill. — In this very important month for the bald eagle, Terrence Ingram is trying to upend conventional wisdom about our majestic national symbol.

He lacks the academic bona fides of an ornithologist but has spent nearly 60 years researching and advocating for bald eagles; he is even credited with saving more than 6,000 acres of eagle habitat along the Mississippi River. In 1995, Ingram established the Eagle Nature Foundation as the successor to a similar organization he’d started nearly three decades earlier.

Counting bird populations like bald eagles can be extremely difficult because of possible duplication. Reuters/Bob Strong

His point is simple: The bald eagle population is declining.

It is an astonishing conclusion that flies in the face – so to speak – of the narrative that presents the bald eagle as a great American comeback story. And Ingram’s theory is particularly noteworthy this month, when federal agencies and about 100 volunteers affiliated with his foundation conduct separate, crucial midwinter bald eagle counts.

“I know, I’m out in left field, huh?” Ingram, 78, said recently from the headquarters of the Eagle Nature Foundation, in a creaky, nearly 150-year-old house that doubles as his insurance office in this tiny town 140 miles northwest of Chicago. “That’s OK. I’ve known that for years.”

Nearly extinct in the early 1960s from the widespread use of the pesticide DDT, habitat destruction and illegal shooting, the bald eagle population reportedly has become so robust since the 1980s that it’s starting to threaten other species, including some rare birds.

The U.S. Fish & Wildlife Service’s best estimate places the bald eagle population at nearly 143,000, a significant jump from 30 years ago, when the service estimated that only 2,475 breeding pairs existed in the entire country.

Sightings of bald eagles and nests have occurred in unusual spots, too. Last summer, an eagle crashed into a Gold Coast hotel window. In the spring of 2016, several were seen soaring and landing in a wide-open park near a landfill on Chicago’s South Side.

There’s also the North American Breeding Bird Survey, taken during summer, that places recent growth at more than 12 percent a year for the U.S. and a whopping 37 percent per year in Illinois. An Illinois Audubon Society count last winter found 2,002 eagles – more than double the number of the birds counted here in 2016.

So how can Ingram justify his conclusion?

He relies on 57 years of midwinter bald eagle counts his organization has conducted along and around the Mississippi River from Wisconsin to southern Illinois. Some years, his volunteer counters reach as far south as Louisiana.

Uneven as the counts are, they show a drop of nearly 400 bald eagles, or 25 percent, from 2010 until last year’s survey through the region stretching from northern Wisconsin to southern Illinois. Ingram also is concerned about a drop in the counts of young eagles, known as “immatures.”

Experts who know of Ingram’s work treat it with respect but skepticism.

“I don’t question Terry’s numbers showing decline,” said Illinois Audubon Society Executive Director James Herkert. “The question for Terry would be what effort has been made to tease out weather and effort? How deep did they go in their analysis?”

Counting birds, as one might imagine, can be extremely complicated. Duplication is a serious concern, particularly in sweeping endeavors like regional or national bald eagle counts in unpredictable winter conditions. So is the experience and commitment of the person counting the birds.

Bald eagles are especially challenging. The easily spooked birds can fly 75 mph. Experts say a 10-mile trip is relatively common, and they have been known to fly as far as 200 miles in a day.

Those factors — as well as climate change, winter weather variances from year to year, abundance of prey and the distance the birds have to fly south to find open, unfrozen water — make every organization’s winter count vary wildly.

“For this reason, it is virtually impossible to tell if downward trends in winter counts are due to declines in bald eagle population size or due to shifts in distribution in response to warmer winters,” Brian Millsap, national raptor coordinator for the Fish and Wildlife Service, said in an email. Several studies show that warmer winters are prompting many raptors to shift their winter distribution, he added.

Midwinter surveys of the Eagle Nature Foundation and Illinois Audubon Society show those wide swings. In 2008, for example, the foundation’s total bald eagle count was 4,052. The next year that number dropped to 2,830. The society’s midwinter count reached an all-time high of 5,597 birds in 2014. Two years later, the count was 946.

“We do not believe that trends in counts of wintering bald eagles indicate overall populations are declining,” Millsap said. “We do value the citizen science contribution of the midwinter survey and recognize it provides important information for management of local bald eagle wintering areas.”

Ingram’s main criticism is that the conventional counts go on for two weeks, which allows for widespread duplication. His organization’s counts run for two hours on one day, usually around Jan. 26.

In addition, Ingram’s theory for why the eagle counts are dropping is that glyphosate, the active ingredient in a widely used pesticide, is making its way through the food chain. The U.S. Environmental Protection Agency’s ecological risk assessment on the compound, released in December, “indicates that there is potential for effects on birds, mammals and terrestrial and aquatic plants.”

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