WASHINGTON (AP) — Wind energy facilities have killed at least 67 golden and bald eagles in the last five years, but the figure could be much higher, according to a new scientific study by government biologists.

The research represents one of the first tallies of eagle deaths attributed to the nation's growing wind energy industry, which has been a pillar of President Barack Obama's plans to reduce the pollution blamed for global warming. Wind power releases no air pollution.

But at a minimum, the scientists wrote, wind farms in 10 states have killed at least 85 eagles since 1997, with most deaths occurring between 2008 and 2012, as the industry was greatly expanding. Most deaths — 79 — were golden eagles that struck wind turbines. One of the eagles counted in the study was electrocuted by a power line.

The vice president of the American Bird Conservancy, Mike Parr, said the tally was "an alarming and concerning finding."

A trade group, the American Wind Energy Association, said in a statement that the figure was much lower than other causes of eagle deaths. The group said it was working with the government and conservation groups to find ways to reduce eagle casualties.

Still, the scientists said their figure is likely to be "substantially" underestimated, since companies report eagle deaths voluntarily and only a fraction of those included in their total were discovered during searches for dead birds by wind-energy companies. The study also excluded the deadliest place in the country for eagles, a cluster of wind farms in a northern California area known as Altamont Pass. Wind farms built there decades ago kill more than 60 per year.

"It is not an isolated event that is restricted to one place in California, it is pretty widespread," said Brian Millsap, the national raptor coordinator for the U.S. Fish and Wildlife Service, and one of the study's authors.

The study excluded 17 eagle deaths for which there was not enough evidence. And, in a footnote, it says more golden and bald eagles have since been killed at wind energy facilities in three additional states — Idaho, Montana, and Nevada.

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It's unclear what toll the deaths could be having on local eagle populations. And while the golden eagle population is stable in the West, any additional mortality to a long-lived species such as an eagle can be a "tipping point," Millsap said.

The research affirms an AP investigation in May, which revealed dozens of eagle deaths from wind energy facilities and described how the Obama administration was failing to fine or prosecute wind energy companies, even though each death is a violation of federal law.

Documents obtained by the AP under the U.S. Freedom of Information Act show that in two cases in Iowa federal investigators determined that a bald eagle had been killed by blunt force trauma with a wind turbine blade. But neither case led to prosecution.

In one of the cases, a bald eagle was found with a missing wing and a leg in a corn field near a turbine at EDP Renewables North America LLC's Pioneer Prairie facility in Iowa. But the report says, "due to the sensitive nature of wind farm investigations and the fact that this investigation documented first violation for EDPR in Midwest, no charges will be pursued at this time." The report lists four other golden eagle deaths at a wind farm operated by the company in Oregon. The company did not return emailed questions about the incidents from the AP.

The Fish and Wildlife Service, which employs the six researchers, has said it is investigating 18 bird-death cases involving wind-power facilities, and seven have been referred to the Justice Department. The authors noted the study's findings do not necessarily reflect the views of the agency, although some of their data was obtained from staff.

Meanwhile, the wind energy industry has pushed for, and the White House is currently evaluating, giving companies permission to kill a set number of eagles for 30 years. The change extends by 25 years the permit length in place now, but it was not subjected to a full environmental review because the administration classified it as an administrative change.

Wind farms are clusters of turbines as tall as 30-story buildings, with spinning rotors as wide as a passenger jet's wingspan. Though the blades appear to move slowly, they can reach speeds up to 170 mph at the tips, creating tornado-like vortexes.

Wind farms in two states, California and Wyoming, were responsible for 58 deaths, followed by facilities in Oregon, New Mexico, Colorado, Washington, Utah, Texas, Maryland and Iowa.

In all, 32 facilities were implicated. One in Wyoming was responsible for a dozen golden eagle deaths, the most at a single facility.

The research was published in the Journal of Raptor Research.

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