Bald Eagles: A Majestic Mystery

There’s a mystery surrounding Colorado’s bald eagles. They migrate through Colorado every year, but recently they’ve migrated away from a favorite site.
Bald Eagle
Bald Eagle. Photo by © Wayne Lewis/CPW.

Mystery surrounds bald eagles as CPW parks celebrate the national symbol.

There’s a mystery surrounding Colorado’s bald eagles. The birds migrate through Colorado every year by the hundreds, roosting, hunting, fishing, nesting and producing new chicks. But recently they’ve migrated away from a favorite viewing site and no one is quite sure why.

Just 25 years ago, so many bald eagles congregated at Lake Pueblo State Park, in Colorado Parks and Wildlife’s (CPW) southeast region, that a winter festival was created to celebrate the majestic national symbol.

But something strange has happened. These days, it’s getting hard at Lake Pueblo to find any bald eagles, instantly recognizable with their distinctive white heads and tails accenting their dark brown bodies and wings, and their piercing eyes looking down over imposing hooked yellow beaks.

“We’re seeing fewer than normal,” said Ed Schmal, a conservation biologist in CPW’s Pueblo office. “In the 1990s, we had hundreds of bald eagles here in the winter. Now, we’re lucky to see 10 or 15. Some years are better.”

Bald Eagles at Lake Pueblo State Park
Bald Eagles at Lake Pueblo State Park.  Photo by © Vic Schendel/CPW.

Don’t worry. The disappearance of bald eagles from Lake Pueblo does not signal a return to dark days of the 1970s when just 450 pairs of bald eagles remained in the continental U.S. and only 10 pairs existed in Colorado.

Bald Eagle Populations

Bald eagle populations plunged during the 20th century due to use of pesticides like DDT and the loss of nesting habitat as the U.S. population soared and cities and suburbs sprawled.

Today, bald eagles stand as a huge conservation success story. Government protection from illegal shooting, the banning of DDT and other dangerous pesticides and a commitment to habitat preservation helped them rebound. As a result, they have reclaimed their historic North American range, especially across Canada, Alaska and other northern states.

In fact, bald eagles now can be seen, in varying densities, in all 50 states, most commonly along large rivers, dams and reservoirs near open water and where tall trees offer their preferred perches.

Tracking Eagle Nests

In Colorado, CPW biologists are closely tracking nearly 200 active bald eagle nests: 113 in the northeast region, 61 in the northwest region, 20 in the southwest and six in the southeast. That’s a huge improvement from the mere 10 pairs that remained 40 years ago.

But look closely at those numbers. Why are there just six bald eagle nests in the southeast region of Colorado? And just 26 in all of southern Colorado?

Combine the lack of active nests with the disappearance of communal winter roosts ­— usually several miles away from any nests, which are fiercely defended by mating eagles — and you have yourself a bona fide mystery.

Biologists can only theorize why bald eagles are thriving across northern Colorado but seem to be avoiding the southern half of the state and the southeast, in particular.

“They might not need to migrate this far south because the northern states are warmer now,” suggested April Estep, CPW wildlife biologist in the agency’s southeast region headquarters in Colorado Springs. “Perhaps they are finding bigger open ponds up north. Why waste energy flying south if they have open water up north?”

Nesting Year-round

That said, Estep believes there are more nests in the southeast than biologists have been able to document, and she notes the eagles in the southeast tend to stay in their nesting territory year-round rather than migrate away in summer.

Estep said there could be other reasons besides the climate-change theory, which has been argued by the National Audubon Society and other advocacy groups.

Mike Sherman, a wildlife biologist in CPW’s northeast region, offered his own ideas about the disappearance from Lake Pueblo and general scarcity of bald eagles in southeast Colorado.

“Communal roosts are very dynamic,” said Sherman, a raptor specialist. “There are historic areas where they communally roost. But they can move from one set of trees to another over a period of years.”

Human Disturbance

Human disturbance can cause eagles to relocate. An increase in winter activity by humans in a nesting or roosting area at Lake Pueblo could have scared off eagles, Sherman said.

“It can be as simple as more boat traffic, or a new recreation trail or a parking lot,” he said.

Or the disparity in documented nesting sites and winter roosting areas could have an even simpler explanation.

“It could be that we have better detection in the north,” Sherman said, noting the South Platte flows through the densely populated Denver metropolitan area with its enthusiastic population of citizen scientists and bird-watchers.

Partners & Volunteers

Even the efforts of CPW biologists have tilted north, historically. CPW biologists first started aggressively tracking bald eagles in the northwest region in the 1980s and built a network of volunteer spotters and a computer database that soon spread to the northeast.

“Our biologists in the northwest made a big effort to search for raptor nests and enlisted biologists at the U.S. Forest Service and the Bureau of Land Management to search,” Sherman said, noting it wasn’t until the early 2000s when CPW went statewide with its raptor nest database.

 Pair of bald eagles perched near a nest at Barr Lake
Pair of bald eagles perched near a nest at Barr Lake. Photo by © Vic Schendel/CPW.

CPW biologists even built artificial steel nests that they erected in trees to attract mating eagles. The first pair set up housekeeping in an artificial nest at Barr Lake in the South Platte River valley northeast of Denver in 1986 and began fledging eaglets.

Barr Lake’s Eagles

“We’ve always had a nesting pair since 1986,” said Michelle Seubert, CPW’s park manager at Barr Lake State Park. “And we’ve had 54 eaglets fledge from Barr Lake.”

Seubert said dozens of bald eagles enjoy a communal roosting area at Barr until the park’s nesting pair decide to lay eggs, usually around Valentine’s Day. Then the pair, who mate for life, drive off all other eagles from their territory and settle in for a 35-day incubation period in which the eggs are never left alone in the nest.

“It’s a good time to see the eagles because there will always be one eagle on the nest,” she said.

By about Father’s Day, the eaglets will fledge and continue to remain in the area.

About the same time Barr Lake was adopted as a nesting home for a breeding pair in 1986, bald eagles also discovered Lake Pueblo State Park and the adjacent State Wildlife Area along the Arkansas River.

Smart Choices

Their choice made sense; Lake Pueblo offers prime habitat. The reservoir is a large body of water that remains open all winter, water constantly flows below the dam, there are abundant and varied species of fish and small mammals, and plenty of tall cottonwood trees on which to perch and spy prey.

Bald eagles were a natural addition to the wide assortment of songbirds, waterfowl and birds of prey that already called Lake Pueblo home. The area also is well known for its large population of great-horned owls, abundant red-tailed hawks, ospreys that nest in specially made nest boxes, turkey vultures, prairie falcons, kestrels, golden eagles, ferruginous and Swainson’s hawks and even the rare peregrine falcon.

But unlike Barr Lake, bald eagles haven’t nested and bred at Lake Pueblo.

The lack of a nest didn’t seem to matter when visitors had hundreds of bald eagles to view and enjoy from November, when they first arrived, until March when they leave for their nesting grounds.

The absence of nests matters more now that Lake Pueblo is no longer a favorite communal roosting site.

Wintering in Other Areas

“We used to get dozens of eagles,” said Monique Mullis, CPW’s park manager at Lake Pueblo. “But they are starting to winter in other areas of the state. They are spreading out more.”

Indeed, CPW biologists have received reports of bald eagle nests on Huerfano Lake in eastern Pueblo County as well as on Holbrook Reservoir north of La Junta and farther down the Arkansas, east of Lamar.

Websites like log dozens of bald eagle hot spots up and down the Arkansas, especially at John Martin Reservoir State Park near Lamar, from citizen scientists who have posted data going back years.

Even though Lake Pueblo has lost many of its wintering eagles, there is no loss of enthusiasm for them and the Pueblo Eagle Days festival is a highlight of the region.

“The eagles are awesome,” Mullis said. “They are the stars. But it’s not just about eagles. We talk about birds of prey.”

 Raptor presentation at Lake Pueblo Eagle Days
Raptor presentation at Lake Pueblo Eagle Days. Photo by © Mike DelliVeneri/CPW

Those who attend the family-friendly festival ­— to be celebrated at the Lake Pueblo Visitor Center on Saturday and at the Nature and Raptor Center of Pueblo on Sunday — will find a variety of programs offering fun and discovery for all ages.

All the details are posted on the event’s website, and can be seen on Lake Pueblo’s Facebook page. The events will include live demonstrations of birds of prey, raptor identification programs, a photo contest, a driving tour to spot raptors and even a raptor release of an injured bird that has been rehabilitated and is ready to return to the wild.

Ed Schmal, the Pueblo-based biologist, urges people to seek out the Pueblo Eagle Days festival.

“It’s a great event,” he said. “I’ve been here 13 years and it’s exciting. We set up eagle-viewing stations around the park. The rehabbed raptor release is exciting. It’s just a lot of fun.”

“We’ll have tours into the wildlife refuge and a live bald eagle presentation,” Seubert said. “We’ll have kid’s crafts. And the Friends of Barr Lake will be doing an ‘Adopt an Eagle’ program. Participants can buy a stuffed animal for $35. They will get an adoption certificate and then a volunteer will send them updates throughout the year.”

Immature bald eagle in flight. Photo by © Mike DelliVeneri/CPW

The festivals are designed to further CPW’s mission to perpetuate Colorado’s wildlife as well as educate and inspire current and future generations to serve as stewards of our natural resources.

Maybe one of them will grow up and solve the mystery of the missing bald eagles at Lake Pueblo.

This article was written by Bill Vogrin for the January/February issue of Colorado Outdoors Magazine. Vogrin is a public information officer for the Colorado Parks and Wildlife southeast region. CPW is a proud partner of the” Year of the Bird.”

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