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Bald eagles made a comeback, but golden eagles face an uncertainty  

Credit:  Christine Peterson | Casper Star Tribune | February 23, 2020 | trib.com ~~

In the 1960s, after years of bald eagles dropping dead across the country due to DDT, the creatures were listed as endangered. If nothing changed with pesticide use, researchers said, bald eagles would simply cease to exist in many areas.

Golden eagles, on the other hand, never faced that kind of crisis point. Bald eagles subsisted off of fish and waterfowl that ate insects infected with DDT. Golden eagles ate rabbits and prairie dogs.

Their numbers had diminished – the federal government at one point ran an extermination campaign on behalf of the livestock industry – but golden eagle numbers eventually stabilized.

Until now. Or rather, until what is to come.

Unlike bald eagles that faced one enemy and are now flourishing, golden eagles’ future is murky because of a virtual buffet of problems from wind turbine blades to power lines to lead bullet fragments left over from big game carcasses.

Solutions to the problems are equally murky and scattered, which is why the U.S. Fish and Wildlife Service began the Western Golden Eagle Team, and hired eagle experts like Zach Wallace, a biometrician with the Wyoming Natural Diversity Database and Bryan Bedrosian, a research director with the Teton Raptor Center, to compile reports of the myriad risks golden eagles face and also possible answers. Those reports were recently released to the public, and Wallace and Bedrosian hope they will be a guide for nonprofits, wind farm developers, state agencies and others to better understand the plight of the eagle and create a conservation plan.

“I am cautiously optimistic. I think we have a big challenge ahead of us, in Wyoming particularly, with the industry growth of wind power,” Bedrosian said.

***

Like sage grouse, pronghorn and even grizzly bears, Wyoming has been a haven for golden eagles. In fact, northeast Wyoming has up to 24 times the nesting density compared to lower quality habitats, Bedrosian said, and the Powder River Basin holds about 23 percent of the total habitat for golden eagles in the northwest plains.

The habitat is partly geographic circumstance and partly a decided lack of humans and development.

Golden eagles require massive spaces to roam around and find food – subsisting largely on rabbits, prairie dogs and carcasses.

They like wide open spaces, but they also want something high enough upon which to perch.

“If you think about Wyoming, we have a lot of variation in our terrain and a lot of sagebrush and prairie, but anywhere you are you don’t have to look far for a cliff or lone cottonwood for a nest site,” Wallace said.

But because they roam so widely, they’re particularly susceptible to wind turbine blades. According to the U.S. Fish and Wildlife Service, collisions, which include everything from wind turbines to car accidents, killed more than 540 birds a year between 1997 and 2013.

Electrocution was also high on the list, killing on average more than 500, largely because their exceptional wingspan of about 6 to 6.5 feet means they’re more likely to touch two wires and complete a circuit.

Golden eagles – unlike bald eagles that spend much of their time in riparian areas eating fish – are also more vulnerable to vehicle collisions as they munch on roadkill on the sides of highways and, in particular, increased traffic on rural roads.

Neither electrocution nor collisions compared to the average number of birds shot – 926 – or killed by poison – 1,025 – each year. And all of those were less than birds that died from starvation or disease, which killed, on average, more than 1,330 birds each year.

That’s where concerns about lead poisoning – largely from lead fragments deposited in big game carcasses during hunting season – comes in.

The lead issue is a controversial one in the nation’s hunting community – proponents of a lead ban say any effort to not kill eagles and other raptors is a worthy one, opponents say lead poisoning, relative to all other eagle threats, is just not that big a deal.

Lead doesn’t directly kill as many eagles as, say, shooting, said Bedrosian, but it likely indirectly kills many more than is estimated.

Low levels of lead poisoning slows an eagle’s ability to react to possible threats like power lines and wind turbines. It also hurts an eagle’s ability to hunt effectively, leading to a documented death by starvation instead of actual lead poisoning.

“You can walk away from your gut pile knowing you did not kill an eagle, or knowing you may have,” Bedrosian said. “The ballistics are there. The cost is nominal. For me (switching to non-lead ammo) is a no brainer.”

Adult eagle deaths are a bigger issue than other species, such as rabbits, because eagles live to be in their 30s and don’t reproduce until they’re at least five years old. Start knocking individual eagles out of a population and the impact can be great.

***

In addition to changing bullets, Wallace and Bedrosian outlined a host of other ways eagle deaths could be curbed.

Some options, like siting wind energy facilities away from high-quality eagle habitat and instead in lower-quality habitat, might not be feasible everywhere. But if not, companies are creating new technologies such as remote cameras on turbines that stop blades when eagles are nearby.

“Given projected increases in development of wind power resources in Wyoming by an order of magnitude over the next decade, effective avoidance and mitigation of turbine-strike mortalities will be critical to maintaining golden eagle populations in the region,” the conservation report reads.

Other options include retrofitting power poles to cut down risk of electrocution and moving roadkill animals away from sides of highways and roads. Research shows that roadkill carcasses are an important source of food for golden eagles, especially young ones in the winter, and scientists in Utah and western Wyoming are trying to figure out how far a carcass has to be moved from the road to eliminate the threat of collision.

“We actually have the risk assessment maps that could help managers identify where the risk is higher in the region and where you could get the biggest bang for your buck for management or conservation dollars,” Wallace said. “We’re predicting a decline in populations, and in theory, that’s already happening, but we’re at the top of the hill, and we can stop it now with some conservation work.”

Source:  Christine Peterson | Casper Star Tribune | February 23, 2020 | trib.com

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

The copyright of this article resides with the author or publisher indicated. As part of its noncommercial effort to present the environmental, social, scientific, and economic issues of large-scale wind power development to a global audience seeking such information, National Wind Watch endeavors to observe “fair use” as provided for in section 107 of U.S. Copyright Law and similar “fair dealing” provisions of the copyright laws of other nations. Send requests to excerpt, general inquiries, and comments via e-mail.

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