The FWS, which investigates deaths of the species, protected under the Bald and Golden Eagle Protection Act (BGEPA), has "credible evidence" of 85 eagle deaths at 34 wind farms in ten states since 1997.
However, five of these investigations are current and most of the fatalities have been in the past three years, according to Scott Flaherty, deputy assistant regional director of external affairs at FWS. This is due to the growing number of wind farms, he said.
The actual number of fatalities is probably higher, as not all deaths are reported to the FWS. The service will publish a state-by-state breakdown of the data in September.
The FWS is encouraging wind farm developers to contact it early in the planning stage of a development to discuss project siting and design and identify potential risks to eagles and other birds and wildlife.
It would like companies to apply for an "incidental take" permit. This effectively allows a company to kill bald or golden eagles, but only if this is incidental to a lawful activity and cannot be avoided.
Although there is no legal requirement to have such a permit, companies that operate without one risk prosecution under the BGEPA if an eagle is killed. Violations of the act by companies carry a maximum fine of $200,000.
"Our goal is to get all of these companies that operate wind farms in the Techahapi and Southern California [region] to come in and talk to us about obtaining a permit. That will help protect them and the eagles. It's in everyone's interest that they have permits," said Flaherty.
Eagle-take permits were created under the BGEPA in 2009. The FWS has not yet issued any eagle-take permits, for wind or any other industry. In California, the state with the highest number of eagles killed by wind turbines, the FWS is working with four wind energy companies and one Native American tribe to develop eagle conservation plans that will lead to applications for permits.
Shawn Smallwood, an ecologist and expert on bird deaths and wind turbines in the Altamont Pass, California, said: "I am certain that golden eagle fatalities have increased."
The magnitude of the problem is not known, because most new projects are either not monitored, monitored inadequately, or the results are not made public, he claimed.
"All of this is unfortunate. The golden eagle is the species that has so far benefited the most from careful siting of wind turbines to minimise collision risk," he said.
John Anderson, director of siting policy at the American Wind Energy Association, said his organisation supported the principle of take permits, but that they are not fully implementable yet.
Although the rule was announced in 2009, guidance was only finalised last month and, according to Anderson, it has not been clear what companies need to do in order to be granted a permit. "It's a bit of a free-for-all at the moment," he said. "We've expressed concerns over that to the service over the last several years."
The FWS already has a long-standing permitting programme under the Endangered Species Act. "Rather than trying to recreate the wheel, they should be relying heavily on the Endangered Species Act permitting process, and instead they have created this separate silo," said Anderson.
The American Wind Wildlife Institute (AWWI) — a collaboration between wind companies and science and conservation bodies — is developing a database to aid evaluation of the impacts of wind farms on wildlife. Data will be anonymous and not linked to one company or project, to resolve industry concerns over commercial confidentiality. AWWI hopes to be able to start producing analytical reports from next year.
"We expect that when it is completed, it will be a very useful tool in answering many of the questions on the impact of wind turbines, or lack thereof, and what areas of research need to be undertaken," said Anderson.