Bald Eagle study

Reesa Conrey releases a bald eagle along the St. Vrain River, July 3, 2021

Colorado Parks and Wildlife announced Tuesday a four-year study on bald eagles in the Front Range to learn about their populations trends and human impact. 

The state park department will look at the national bird from the Denver-metro area up to the Wyoming state line. As of last year, more than 90 breeding pairs of bald eagles are currently living in the corridor, according to a news release.

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"The reason we are focused on this area is the concentration of bald eagles along the Front Range, juxtaposed with the concentration of humans and human infrastructure along the Front Range," said CPW Avian Researcher Reesa Conrey. "That intersection is a huge part of this project, in addition to monitoring what the eagles are doing in terms of their nest numbers and nest success."

The Front Range corridor of northern Colorado has been experiencing rapid growth as the population has gown 18% since the turn of the century, according to officials.

This trend is unlikely to stop as officials estimate the Centennial State to grow by 832,000 with 87% of that happening in along the Front Range. 

Like humans in Colorado, populations of the American bald eagle have also grown as their total numbers in the country have quadrupled since 2019, according to a new report by the U.S. Fish and Wildlife Service.

This is a huge increase from the end of the 1970s where there were only three known nests in Colorado -- none of which were on the Front Range, according to the news release.

In 1972, protections were implemented to save the national bird and the recovery process began, and has accelerated in Colorado over the past few decades. 

Bald eagles utilize the state's reservoirs, rivers and streams that are surrounded by large cottonwood trees and riparian areas that provide ideal locations to nest along the South Platte River Basin, officials said. 

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Discovery of new nesting locations has revealed to officials that bald eagles are relocating from their conventional nesting locations, and hope the study explains why they are doing so.

"We are looking at nest sites along a gradient of human activities and disturbances from urban to rural areas," Conrey said. "We are especially interested in comparing areas expected to remain stable with new development within the next few years.

"We can use spatial data over the past several decades to get a land use change as this area has been developed for residential and commercial use, agricultural conversions, sand and gravel mining and energy, including oil and gas wells, solar, and wind energy facilities. We're getting more transmission lines, cell towers, road traffic, use of trails and boating areas and all the other things that go along with human activity and an increasing human population."

Officials will be placing GPS transmitters on the 20 to 30 birds -- that will be able to provide frequent location data in as little as four seconds between locations. 

The trackers are different than what the state parks and wildlife department generally use as they're missing an antennae to connect to satellite networks. However, with advances in technology the new transmitters can connect to cellar communication networks, officials said.

"It allows our transmitters to be lighter in weight," Conrey said. "That reduces potential stress on the eagles, and it was a good choice for us in the Front Range because we have a lot of cell towers in this area."

Trackers began being placed on the birds earlier this month and will continue in a second-round in October.

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Many volunteers from the Bird Conservancy of the Rockies, and staff from city, county state and federal agencies will assist in the study. 

"This gives us an opportunity to put (increased human and bald eagle data) to work and learn more about how eagles are adapting to the changes we're making to the landscape," said Matt Smith, outreach biologist with Bird Conservancy of the Rockies. "Hopefully, this will tell us more about what the future looks like for bald eagles in the years to come and what management action can be undertaken to ensure a healthy population of this iconic bird in our state."

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