Robert J. Galbraith Special to the Montreal Gazette, August 2014.

MONTREAL — Once a rare sight in Quebec, bald eagles are thriving across the province, and the surge shows no sign of a slowdown as these magnificent raptors re-populate our rivers, lakes and shorelines.

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Reduced to a mere half-dozen nesting birds in the 1970s, there are now more than 200 bald eagle nests producing offspring, and those numbers are climbing fast as the young disperse across the province, taking over former nesting sites and setting up new territories. Researchers predict they might eventually start settling in and around Montreal.

For a bird that was extremely rare just a few decades ago, this is a stunning recovery, and the bald eagle’s resurgence, in Quebec and across North America, is an example of humans successfully stepping in to help an endangered species.

At their peak, bald eagles may have once numbered in the thousands across Quebec from Anticosti Island to Abitibi and from the southern tip of James Bay to the waterways of southern Quebec, with the highest population along the St-Lawrence and Ottawa Rivers.

However, bird of prey populations went into freefall with the worldwide introduction of the pesticide DDT (dichlorodiphenyltrichloroethane) for agricultural use in 1945.

DDT was supposed to be the insecticide that would save the world’s food supply from insects, and so it was sprayed on everything from vegetable crops to marshlands in order to control mosquitoes. Toxic to humans and wildlife, it was banned in North America the 1970s. Bald eagles exposed to DDT tended to lay thin-shelled eggs that broke during incubation.

While the bald eagle’s subsequent turnaround is largely attributed to the DDT ban, there were other factors at play, including a captive breeding program and a shift in attitudes that led to an increase in public pressure to preserve the environment and its wildlife.

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Another for the bald eagles has been an increase in Quebec’s deer population, meaning more roadkill and deer carcasses in general — the principal source of winter food for the eagles when lakes and rivers are frozen over.

Research from the Quebec Breeding Birds Atlas, which maps bird movements and populations within the province, shows that as bald eagles re-establish former habitats and take up new territory, a great number of the province’s lakes, rivers and reservoirs could become home to the birds over the next two decades.

Researchers and bird enthusiasts who help document bird migration and distribution for the Atlas and other bird publications have found that since the 1970s, bald and golden eagles have been more than doubling every 10 years in Quebec. At one site known as Eagle Crossing near Vaudreuil, eagle numbers have been counted and documented each spring for the last 40 years.

Pointe Claire resident Bob Barnhurst, a retired metallurgist, is part of the small army of dedicated volunteer researchers who contribute their time and expertise to count birds of prey during spring migration. He has witnessed the increase first-hand, over his 36 years of observing and counting eagles and other raptors in Quebec.

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“One of the great successes in conservation over the last half-century has been the comeback of the bald eagle. All of this is largely the result of the elimination of DDT from the environment. And these birds have come back at such an extent that we are getting much larger numbers everywhere, not just in migration but breeding in Quebec and across the entirety of North America,” explained the veteran bird observer.

Pesticide use wasn’t the only culprit blamed for the falling numbers over the last 200-plus years. Habitat destruction, hunting, lead poisoning, collisions with hydro lines and wind turbines, trapping and disturbance at nest sites were other major problems that to some extent continue to hinder recovery efforts.

Barnhurst says the migration studies have shown that each year, more and more of the birds are raised and survive than the previous year.

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In the early 1970s, there were fewer than 10 known active nest sites in the entire province, according to provincial and federal biologists who study bird species, numbers and movements. In 1989, that number had climbed to approximately 30 nesting pairs. As of this year, researchers have confirmed 200 active nests and just as many occupied territories that could become nest sites.

As wildlife enthusiasts rejoice in the resurgence of this majestic bird, researchers caution that we must not to love them to death.

“They are very sensitive to disturbance, especially during the first nesting attempts, so we need to leave them alone so they can successfully nest and not be disturbed, which could lead to the birds abandoning their nest before they get a foothold,” explained U.S. Fish and Wildlife Service biologist Judy Edwards. She works at the Missisquoi Wildlife Refuge in Swanton, Vt., on the shores of Lake Champlain’s Missisquoi Bay.

This site, about 100 kilometres southeast of Montreal, is one of the places where the eagle boom is most evident. “For the last four years we’ve had nesting bald eagle on the refuge, and every year since then there has been success producing chicks.”

With more than 130,000 rivers and one million lakes and waterways in Quebec, there is no lack of nesting space available for Canada’s largest bird of prey. The birds like to net up nests near large bodies of water that act as a source of food, and prefer large, old trees.

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“In 20 years, the birds might well be found breeding in populated areas, maybe Île Bizard or places like it with big populations of people and access to water and perching trees for eagles,” explained Michel Robert, a biologist with the Canadian Wildlife Service in Quebec, and coordinator of the Quebec Breeding Bird Atlas project.

“I often see a pair very close to Quebec City along Champlain Blvd., not far from where I live, along the river. I am quite sure they are nesting quite close to the city, but I haven’t found a nest yet. Yes, we may well be surprised to see them living near populated areas in the coming decades.”

Eagles could eventually nest in Montreal proper. Just a few years ago, a pair nested on Heron Island, in the Lachine Rapids.

To find out whether bald eagles have been spotted in your area, or to track the presence of other bird species in Quebec, go to www.atlas-oiseaux.qc.ca, click on “interactive tools” and choose “Atlas results.”