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Colorado bald eagles can swim, CPW research finds — The Know

Bet you didn’t know bald eagles can swim. Neither did Reesa Conrey, an avian researcher for Colorado Parks and Wildlife who is leading the most comprehensive bald eagle research project the agency has ever conducted.

Sure enough, Conrey saw it happen on Tuesday: A bald eagle doing the breaststroke.

“I learn something new every day,” Conrey said. “I was out looking for one of our tagged birds and I saw a juvenile swimming. I didn’t know that bald eagles could swim. And they don’t swim like a duck or a goose (paddling), they actually use their wings. My bird was doing what I would call a lazy breaststroke.”

They do have six-foot wingspans, after all, just like Michael Phelps.

“I went home and looked it up on Google, ‘bald eagle swimming,’” said Conrey, who is leading a four-year study by CPW to track Front Range bald eagle trends, habitat use and impacts from human disturbances. “You can see pictures of them doing like a Michael Phelps butterfly stroke, trying to carry a big fish back to shore, so big that they couldn’t launch themselves back into the air from the water.”

There’s another surprise unfolding for Front Range bald eagles, one that must be exciting for fans of the majestic birds. Despite the encroachment of development driven by explosive population growth, the bald eagle population seems to be thriving. Conrey said there are 95-100 “nesting pairs” in the northern Front Range, a remarkable number considering that at the close of the 1970s, there were only three known bald eagle nests in Colorado, and none of them were in the Front Range.

Not everything associated with the growing urbanization of Colorado is detrimental to bald eagles, which like to build nests in trees near large bodies of water.

“We know why the populations took such a dive mid (20th) century, and that was largely due to DDT, the insecticide that is pretty well known to have made eggs thinner,” Conrey said. “It’s hard to say whether it just took this long for the populations to very gradually recover. Also, as humans have moved in, there are a lot of the parts of the Front Range that would have been prairie, and maybe not had a lot of trees, and not all these lakes and reservoirs that we have now.

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“At the same time that bald eagles are losing habitat due to human development, they’re also gaining nest sites because of the reservoirs and the cottonwoods that are around those reservoirs.”

CPW plans to attach tracking devices on 25-30 bald eagles. Solar-powered and lightweight, the trackers ping off cellphone towers. Two eagles were tagged last year, and a dozen more have been tagged over the past two months.

“We’re trying to get a better handle on the trajectory of our bald eagle population, which seems to be pretty successful, but is located in an area that’s really rapidly developing with people moving into the area, recreation, residential development, oil and gas (drilling sites), wind farms. We’re trying to figure out where our eagles are moving and how they’re using this landscape that people are also using.”

An eagle they tagged last summer has flown back and forth to Wyoming at least twice, Conrey said.

“We’ve got a juvenile female tagged right now who has flown up to Saskatchewan,” Conrey said. “The reason the transmitters are useful is because we can follow the birds year-round wherever they go, as long as they ping off a cell tower at some point. I think that will really help us understand what areas they’re using and what areas they might be avoiding.”

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That kind of information will help CPW make recommendations on how new land developments can minimize harmful interaction with the eagle population.

“Our agency is tasked with providing info and guidance to developers, consultants, the general public and all of our partners to make sure that our eagle population continues to be successful,” Conrey said. “And, either continues on that upward trajectory, or stabilizes at a nice healthy level.”

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