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The species’ remarkable ability to adapt is epitomized by a lone bird hard at work – and prey – at City Park. A comeback is taking flight.
A bald eagle is using central Denver as a hunting ground, scanning from perches over City Park lakes for fish, ducks and small geese – evidence of resilience in eagles’ struggle to come back from the brink of extinction. But compared with wild prairie, this 330-acre park provides marginal habitat: loud engines and the beeps of park-crew vehicles backing up, the Denver Zoo complex construction, dog-walkers circling frozen shores and talking into smartphones, and the 82-decibel orange robot “Goosinator” to haze geese.
The eagle in City Park shows bald eagles’ remarkable ability to adapt, said Kevin Kritz, a federal biologist monitoring raptors and eagles for the Division of Migratory Bird Management.
“Bald eagles are a species that has proved to be a lot more flexible in their nesting and habitat than we ever thought possible, and bald eagle populations are expanding,” Kritz said. “Some bald eagle pairs are able to come into cities and make a living.”
The nationwide bald eagle population — once threatened by the DDT pesticide, requiring Endangered Species Act protection until 2007 — has grown to an estimated 143,000. That number increased between 2003 and 2013 by an average 12 percent a year, federal officials say.
However, bald eagles’ less-adaptive cousin, the golden eagle, remains in often-compromised rural habitat. Golden eagles’ population has stayed flat around 40,000 (31,000 in the western United States).
The number of eagles in Colorado is uncertain. Colorado Parks and Wildlife officials say they no longer estimate golden and bald eagle populations. A recent federal report says bald eagle nests in the state increased from 51 in 2009 to more than 125 nests in 2015. Golden eagle data is limited.
“While the U.S. Fish and Wildlife Service remains cautious concerning golden eagle populations, the continued increase in bald eagle numbers is a great success story,” agency spokesman Steve Segin said.
Last year, a fully grown female bald eagle landed near Longmont on power lines
and was electrocuted while her young were still in a nest, according to Brian Smith, the USFWS regional chief of migratory bird management. But another adult female paired up with the male, adopted the young eagles and raised them to where they could fly and hunt.
There’s competition all around for decent habitat for nesting and hunting. Inside metro Denver, developers’ push for denser development — blocks of condominiums and apartments — combined with rapid human population growth strains the existing open space. In once-quiet rural Colorado, a boom in oil, gas and wind energy production edges out eagles and other wildlife.
Balancing the energy development with bird conservation has become a battle, especially with recordfast installation of wind turbines that mangle and kill hundreds of eagles a year in the 170 mph whirling blades. While not endangered, golden and bald eagles are protected under the Migratory Bird Treaty Act and the Bald and Golden Eagle Protection Act, which prohibit killing eagles with- out a permit.
Federal wildlife regulators are honing their approach. The feds say they will negotiate permits in advance, specifying limits on how many eagles can be killed over 30 years – “incidental take” — at energy industrial sites. Fish and Wildlife Service officials told The Denver Post that 4,200 bald eagles a year could be killed without harm to the species.
“What we’re trying to do is manage the ongoing take, and make that legal, and then get conservation benefits in return,” said Kritz, who is helping to negotiate a permit for the proposed $5 billion Chokecherry and Sierra Madre Wind Project near Rawlins, Wyo.
The idea is that companies running wind, highway, oil and gas, and other projects that cause harm to eagles, for which they receive “take” permits to cover accidental killings, “will have to do things: conservation measures, surveys, things that produce conservation benefits for the species,” Kritz said. “With a permitting system, you have a chance to be proactive.”
The Cokecherry wind project in Wyoming initially would deploy 500 wind turbines, project documents show. A permit covering five years hasn’t been issued yet pending discussions over issues such as the size of turbine blades (bigger blades kill and maim more eagles). Federal regulators estimate the Cokecherry wind farm turbines would kill one or two bald eagles and 10 to 14 goldens a year.
Yet it’s unclear exactly how disruptions of traditional eagle habitat may be related to the rise of eagles adapting to living in cities. Most eagles in Denver parks prove to be shorttime visitors. The one in City Park this month was alone. Parks staffers say eagles have not made nests in City Park. Lone eagles have hunted there since 2012.
City officials regard the situation as fragile, urging a hands-off approach to minimize urban disturbances.
“Some people find it surprising that wildlife can be found in and around the urban areas of Colorado’s fastgrowing Front Range,” Parks and Recreation administrator Vicki VargasMadrid wrote in an e-mail. “As our state continues to become more populated, more wildlife species are being displaced and forced out of their natural habitat, resulting in them having to adapt to our way of life, in an urban setting. Certain species of wildlife, of course, are more resilient than others.”