The eagles are the equivalent of tourists, migrating thousands of miles from the northernmost reaches of North America to Wyoming, where they will spend the winter months. Like many tourists, the birds often seek thrills.
They can often be seen floating in the wake of the giant wind turbines that populate these hills, Aldrich said, riding the breeze the blades create like a thrill-seeker rising and falling on a roller coaster ride. When wind operators turn the turbines off, the eagles frequently disappear, he said.
"As biologists, we're taught not to think of animals anthropomorphically, but, I'm sorry, there's no other word for what they're doing. They play," Aldrich said. "You can watch them play in the wind behind the blades, and it's really scary as heck, from my position, to watch."
The crucial distinction between the turbines and a roller coaster is this ride is often fatal for the eagles.
Duke Energy, a North Carolina-based utility, was fined $1 million by the Department of Justice in November for the deaths of 14 golden eagles and 149 other protected species killed by its Converse County wind farms between 2009 and 2013. The fine represented the first time the Obama administration had taken legal action against a wind developer for bird fatalities.
Aldrich is employed by Duke to reduce avian fatalities at its wind farms. The balance of harnessing Wyoming's wind for electricity and preserving the open space that makes the state such good habitat for eagles and other raptors is a challenging one.
Aldrich has spent the last two and a half years studying the behaviors that put eagles at the highest risk of hitting one of the 110 turbines spread across the 17,000-acre Top of the World wind farm outside of Glenrock.
Aldrich used to oversee all of the company's 14 wind farms across the country. Following the fine, his world has revolved around Top of the World and Campbell Hill in Converse County, which produce a combined 300 megawatts of electricity, enough to power 80,000 homes, for Pacificorp.
"Trust me, (Duke knows) there are issues," Aldrich said. "They know it; we're working on it. It's my entire job."
The problem is eagles are an apex predator, which means they are absolutely fearless because they are at the top of the food chain. When they are hunting mode, it's like they have a ball cap pulled down low on their heads that effectively blocks the sun so they can scan the ground for rabbits and other prey. However, the same trait prevents them from seeing anything straight ahead.
Similarly, blaring loud noises to deter them from danger are proving to be ineffective.
"There is technology to deter songbirds from nesting in a substation, but a songbird is not an eagle," Aldrich said. "We need a way to alert them to pay attention. We haven't figured that out yet."
The best solution for now is simply turning off the turbines when an eagle flies within a half-mile to quarter-mile.
Duke is trying to find the quickest, most efficient way to do that. The company recently brought in a radar purpose-built for the military. The technology showed promise over the course of the nine-month test drive, but still suffers from a number of limitations, Aldrich said.
Since radar detects movement, eagles tend to get lost amid the "noise" of the turbine blades. The turbines are 80 feet tall and boast three 40-foot blades. From a distance, they seem to be moving slowly, and they're traveling only about 18 rotations every minute, but the blade tips are actually whirring around at 180 mph. That's too fast for eagles to avoid, and the motion is confusing to radar when the birds fly in front of or behind the turbine.
Another problem is that, sometimes, eagles simply soar too slowly to show up on radar.
Cameras might offer another avenue for locating birds before they get too close.
"Ideally, at some point, it will be automated, but that's, I think, down the road a ways," Aldrich said. "Some companies claim they have that, but until it's proven that's the thing, all of this is so new to us, and a lot of the technology is not proven, and because nobody will talk to each other, it's really, really frustrating."
Fortunately, now that private research and design firms understand the needs of the wind energy market, Aldrich thinks those innovations may start becoming reality.
In the meantime, Duke's eagle monitoring is decidedly low tech.
Dylan Hrkach, 22, of Cheyenne, is what the company calls an eagle watcher. Two are on shift at all times. On a recent, cloudy June afternoon, Hrkach scanned the skies with binoculars from the driver's seat of his company pickup. His feet were kicked up on the dash, and music played softly in the background. If he spots an eagle, he calls headquarters in Charlotte, North Carolina, with a turbine number or general area that needs turned off. The process takes a couple minutes.
Duke is building a 30-foot tower ahead of next winter's migration season. The tower will give watchers a view of every turbine on the grounds, and they'll be able to stop turbines themselves, eliminating some of the delay between observation and action.
Hrkach has been at the job three weeks, and he said he's starting to pick up on some of the tricks for spotting eagles at distances that make the birds look like specks.
Part of it is in understanding the terrain. Each windswept hill has a different personality, providing different levels of lift for eagles depending on the wind's direction, its speed and the temperature. For now, those characteristics are a matter of anecdote, but staff members hope with enough observation and data, they will eventually know where to concentrate their gaze.
"This is basically a research facility," Aldrich said. "The stuff we're learning here will help us build future developments better. We've already said we won't put ourselves in a situation where we can't share the technology. We want to do the right thing, we want everybody else to do the right thing, so you can't keep this stuff secret."
Some wildlife advocates are concerned there are too many secrets surrounding eagle deaths and wind farms.
The American Bird Conservancy has filed two lawsuits against the U.S. Fish and Wildlife Service. One is fighting for greater transparency when it comes to the number of birds killed by individual wind farms. The other concerns something known as an eagle take permit. Companies can apply for the permits, which allow operators to to kill a certain number of eagles without penalty under the Bald and Golden Eagle Protection Act provided they outline plans to reduce avian deaths. The U.S. Fish and Wildlife Service recently extended the life of the permit from five to 30 years. It is considering about a dozen applications from wind energy companies for eagle-take permits.
The American Bird Conservancy said the change was made improperly and without public input.
Michael Hutchins, director of the conservancy's Bird Smart Wind Energy Program, said energy companies self-report mortality rates, making it difficult to get a complete picture of the problem. However, he cited a 2013 research paper in the Wildlife Society Bulletin, which compiled 61 different studies to extrapolate that about 573,000 eagles are killed every year.
Hutchins believes seasonal shutdowns or retrofitting power lines and towers are useful tools for reducing bird deaths once wind farms are up and running. The best strategy, though, is siting the turbines properly in the first place.
"Unfortunately, these things are going up anywhere, including in important bird areas, and we think that's highly problematic," Hutchins said.
The U.S. Fish and Wildlife Service will still review the permits every five years to make sure energy companies are meeting those conditions. Wind developers say the longer permit period will encourage more investment. They note they can take actions like retrofitting power lines so birds won't be electrocuted, disposing of road kill from the wind farm and removing rock piles and other hiding spots used by prey to reduce fatalities. Duke has already implemented those strategies as part of sanctions levied by the Justice Department, Aldrich said.
Perhaps the biggest test of the wind industry's ability to reduce avian deaths will come in Carbon County, where the Power Company of Wyoming has proposed building the largest onshore wind farm in the country - 1,100 turbines generating 2,000 to 3,000 megawatts of electricity.
Researchers there have spent 5,000 hours studying eagles and other birds since 2010, according to Garry Miller, Power Company of Wyoming vice president of land and environmental affairs.
"We've written literally thousands and thousands of pages on this. We've always approached this project from the perspective of using science to inform our decisions," Miller said. "We need a product that's competitive, but it needs to be environmentally responsible. It's not either, or. We can, and are, doing both."
The company has proposed prohibiting wind turbines on 26,000 acres along the North Platte River, and creating a half-mile buffer around eagle nests, according to earlier Star-Tribune reports.
Miller said Power Company of Wyoming has halved the proposed number of turbines and backed off of some of the best wind resources in the region for the benefit of wildlife.
The company is still seeking an eagle-take permit, but Miller said they believe their mapping technology, tracking devices and wildlife studies mean the turbines will be placed where they have the lowest impact to eagles.
"It's a balancing act between developing a project and developing it responsibly," Miller said. "At the end of the day, we are providing electricity, and it needs to be affordable."
If the final stages of permitting go smoothly, Miller expects construction to start in 2015.
The turbines will go up in two phases over an eight-year period. There will be a flurry of activity as the company builds roads, infrastructure and turbines.
Once that activity subsides, however, much of the habitat remains. For better and worse, that means the eagles are still there, too. That means Power Company of Wyoming, like Duke, will have to consider partial solutions like shutting down turbines when eagles fly too close and removing carcasses from the property.
Wind companies are learning on the fly the best way to keep eagles away from turbines without pushing them out of their habitat, but, even as technology improves, Aldrich doubts there will be a single solution. Likely, he said, a combination of automatic emergency shutoffs, deterrents -- whether in the form of sight or sound -- and better planning in the future are all going to be needed.
Renewable energy isn't going anywhere, he pointed out, so it's his job to find the balance between energy production and wildlife protection.