A bald eagle at Barr Lake State Park (courtesy Jason Clay/CPW)

BRIGHTON, Colo. – The cottonwood tree that held a bald eagle nest at Barr Lake State Park was blown down in a windstorm last April, destroying the nest and its two eggs. On Friday, park staff will be installing three nesting baskets back in cottonwood trees to try to entice bald eagles to re-establish a new nest that is in view of the boardwalk gazebo.

Friday’s project will also include the repositioning of the osprey nest platform at the park in addition to the installation of the three eagle nest baskets.

The eagle nest baskets provide a framework that bald eagles may choose when establishing a new nest. The three baskets will go up in different trees located close to each other. They will be mounted using steel cable around tree limbs high up in the selected cottonwoods with a good view of the lake.

Nests can be 7-8 feet across, usually in tall trees high above the ground. Bald eagles often choose dead limbs in tall, mature trees, possibly because their view is not obstructed by foliage. Nests are often found near water.

Females lay one to three eggs, which are dull white. The incubation period is about 35-42 days, with both the male and female sharing egg incubation and feeding duties. CPW avian researchers have found the fledging age in Colorado to be at 10-12 weeks post-hatch.

“We are putting up our starter eagle nest basket in the same area as our last nest tree that fell down in the spring of this year,” said Park Manager Michelle Seubert. “This area is prime habitat for the eagles and provides a way for our visitors to safely view the nest from our gazebo boardwalk. As they say, ‘build it and they (eagles) will come.’ ”

The first bald eagle nest basket was installed at Barr Lake in 1986. Nelda Gamble, who served as the first Bald Eagle Watch program coordinator for the Bird Conservancy of the Rockies, was a volunteer who helped put up that very first nest basket. She will be there on Friday to see the new nest baskets being installed.

“I would not have imagined in 1986 when I first spotted a pair of bald eagles building a nest at Barr Lake State Park I would be still watching the continuing pair today,” Gamble said. “My thanks to the park and its volunteers for 35 years of protecting the nest territory and sharing the story with thousands of children and families.”

That original nest basket installed in 1986 will be one of the three going back up on Friday. It will be the third time putting that original nest basket up at the park since 1986. Although three nest baskets will be installed, it is possible that only one of the closely spaced nest baskets will be used by a pair of eagles because a breeding pair will defend their nest vicinity from other breeding bald eagles. It may also be several years before nesting eagles use any of the three nest baskets.

A pair of bald eagles has been observed in Barr Lake’s wildlife refuge every year since 1986. Since that time, they have survived storms, the loss of nesting trees, and even the disappearance of the male. After three years of failed attempts to raise young, the bald eagle pair was finally successful in 1989. 

As of 2021, the Barr Lake eagles have fledged 59 young eagles. An eagle nest may be added to and reused for longer than 20 years, or a pair may use another nest site. Currently there are two nesting pairs that are residents at Barr Lake State Park. 

“Eagles will likely use a nest for longer than 20 years if the habitat remains adequate and the structure remains stable,” said Reesa Conrey, Avian Researcher for CPW who is leading the agency’s study of bald eagles along the Front Range. “It probably rarely happens in Colorado because of our winds, snow, cottonwood senescence and the eagles’ propensity for building at the tops of dead trees, dead portions of live trees, or other exposed spots.”

A third nesting pair of bald eagles established a new nest about one mile northeast of the park. This additional breeding pair undoubtedly spends time in the park. The presence of three breeding pairs so close to the lake speaks to the high productivity of the park’s water resources and to the expanding bald eagle population in Colorado.

The breeding pair of eagles that used the former nest tree have started a replacement nest elsewhere in the refuge out of view of the gazebo. Park staff and volunteers will be monitoring the fate of their nest-start in 2022. Conrey said that eagles sometimes will maintain more than one nest structure within their territory.

“They may use this new natural, unsupported nest or one of the new nest baskets in 2022, perhaps switching in future years,” Conrey said. “Hard to say which they’ll use in 2022. Bald eagles commonly have two or more alternate structures that they build and tend. These baskets give the eagles more options with more structural security at a windy site, in addition to the nest they began building after their previous nest was lost.”

The Barr Lake boardwalk is situated over the park’s beautiful wildlife reserve, where green tree canopies and glittering waters overwhelm the senses. The best viewing of the previous eagles’ nest was from the gazebo, only a 1.3-mile walk south of the park’s Nature Center into the wildlife refuge. The nest is approximately a quarter mile from the gazebo and is easily seen with binoculars or the spotting scope available at the gazebo.

The gazebo offers photographers and bald eagle enthusiasts an accessible spot to view the eagles without disrupting the nest. That is one reason park staff would like to try and help the bald eagle nesting pairs re-establish a nest in that location, by placing the baskets back up in a new tree by where the previous one was blown down last April.

Photos Below
Row 1, Left Photo: Picture of one of the bald eagle nest baskets that will be installed Friday. This is the original nest basket that was first installed in 1986. (courtesy CPW)
Row 1, Right Photo: Jerry Craig, former raptor biologist with CPW, holds up the eagle nesting basket that was first installed at Barr Lake State Park in 1986. (courtesy CPW)
Row 2, Left Photo: The bald eagle eggs that were destroyed last April when the nesting cottonwood tree was blown down in a windstorm. (courtesy CPW)
Row 2, Right Photo: Picture of the cottonwood tree that was blown down in the April 5, 2021 windstorm, destroying the most recent active bald eagle nest and its two eggs. (courtesy CPW)