Bald eagles are popping out in healthy numbers around Colorado, where historically they were rare, a dramatic adaptation that lifts spirits. State wildlife biologists once deemed such a comeback impossible. Damming rivers to form reservoirs lured geese, created cottonwood nesting habitat and put water year-round in the South Platte River, which otherwise ran dry in late summer.
Using the deadly pesticide DDT was banned. Bald eagles augmented their fish-and-fowl diet by snapping up prairie dogs. And bald eagles proved increasingly resilient amid rapid urbanization.
But new survival struggles loom for their golden eagle cousins. Traditionally far more abundant, golden eagles face intensifying threats – from drought, wind-power turbines, the oil and gas boom and rampant foothills homebuilding that disrupts foraging.
Colorado Parks and Wildlife officials estimate there are more than 115 breeding pairs of bald eagles statewide. Roughly five new nests are documented each year, some on the busy Front Range.
“To have bald eagles come back in numbers where you can see them on a regular basis, that’s an amazing thing – a bird that was going extinct,” Rocky Mountain Bird Observatory staff biologist Jeff Birek said. “Among things in nature that bring awe and wonder to us, eagles are at the top of the list. They’re magnificent. They represent a wildness we long for in today’s society.”
Meanwhile, whirling turbine blades and electrical lines running to oil and gas facilities and wind farms have been linked to golden eagle deaths. Nobody has a good handle on how many eagles and other raptors are caught in blades or electrocuted; scientists have calculated in peer-reviewed articles that turbines kill at least 60 to 65 golden eagles a year nationwide.
U.S. Fish and Wildlife Service officials say they’re ramping up efforts to track eagle mortality. That agency now issues permits to allow limited, unintended killing of eagles for up to 30 years. Companies receiving permits must “mitigate” by fully offsetting harm, adjusting plans in ways likely to save eagles.
Last week, the Department of Energy issued a formal request for ideas to deter eagles from flying into energy industry facilities.
Colorado wildlife biologists, too, favor increased monitoring of golden eagles and research on energy industry impacts.
“Bald eagles continue to do really, really well. We get several reports each year of new nests. We have very robust wintering populations,” said Dave Klute, CPW’s bird conservation coordinator.
“Goldens we know much less about and there is concern, throughout the Western states, about impacts of energy development – oil and gas and wind energy development,” Klute said. “Hopefully, there can be some siting adjustments made to minimize those impacts.”
Nests popping up
Back around 1978 – after federal authorities banned the DDT that thinned eggshells and listed bald eagles as an endangered species – Colorado was given a recovery target of 10 nesting pairs, recalled Jerry Craig, a longtime state raptor biologist, now retired and consulting for the energy industry.
“I told them they were nuts,” Craig said.
Bald eagles rapidly exceeded that target. This past month, Craig marveled at 10 nesting pairs near Durango and another six near Cortez.
Nests have popped up at Denver’s City Park Golf Course, near Evergreen Lake and right next to E-470 in Commerce City.
“The future for bald eagles is rosy,” Craig said.
But golden eagles likely will decline.
“All along the Front Range in their habitat, we’ve got housing development. Golden eagles are not as tolerant as bald eagles,” Craig said. “They’re losing nest sites with urbanization and losing foraging habitat. And now we are sticking these obstacles out there – the wind towers.”
A century ago, Colorado had no significant population of bald eagles. Until the 1970s, eagles deemed threats to lambs and calves could be shot. When the federal government banned the use of DDT in 1972, there were no documented bald eagle nesting sites.
By 2007, federal officials were removing bald eagles from the endangered species list. Two years later, Colorado took them off the state’s list of threatened species.
Still, under federal law, killing any eagle without a permit is illegal.
And government monitoring of eagles has decreased during the nation’s push for domestic energy production. For the past five years, Colorado wildlife managers have not conducted comprehensive surveys of bald eagle nests. Nor have they closely tracked golden eagle populations. (CPW does maintain a database of nesting locations that they refer to when commenting on proposed energy projects.)
The U.S. Fish and Wildlife Service has determined that, from 2006 to 2012, golden eagle populations around much of the West, including western Colorado, have not decreased overall. But some subsets may be in decline.
Threatened by blades
Golden eagles nest in high cliffs. They rely on the same windy updrafts energy companies try to tap. In Colorado, those near Meeker eat jack rabbits. Golden eagles in Front Range foothills forage on magpies, porcupines, snakes, grouse and squirrels.
While drought and electrocution rank among myriad perils, the Department of Energy request last week focuses on ideas for keeping eagles out of wind-turbine blades.
Painting blades bright colors, attaching whistles at ends of rotating blades and otherwise emitting dissuasive sounds have been considered as possibilities in the past – but are not tested.
One company has resorted to posting guards with binoculars at turbine towers – where they can warn operators to shut off turbines if eagles approach, said Karin Sinclair, a project leader at DOE’s National Renewable Energy Lab.
“The wind industry is doing the best they can to responsibly build facilities,” Sinclair said.
The Colorado Wildlife Federation opposes any sort of quota on how many eagles an energy producer could be allowed to kill.
“All energy producers should be required, by both federal and state agencies, to meet the same standards to avoid killing eagles and other birds,” federation spokesman Todd Malmsbury said. “And they should be ordered to use the very best industry practices to prevent the destruction of our native wildlife species.”
American Wind Energy Association leaders said eagle and other raptor collisions with turbines are relatively rare.
“This is not insurmountable at all,” said John Anderson, AWEA’s director of siting policy.
“Every form of energy has an impact on the environment. You can’t look at one potential impact of one industry in isolation and get a sense of the best interest of society and the environment,” Anderson said.
“We fully expect that, over time, impacts to eagles and other wildlife will be reduced while allowing for robust development across the country. This will be achieved through creative thinking and improvements in siting.”
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