While the number of bird deaths caused by wind turbines is small compared to other threats like cars and power lines, the wind industry's impact on wildlife remains under scrutiny.
The latest example came last month, when an Associated Press investigation concluded that the Obama administration is giving a pass to the wind industry by not prosecuting wind farms when eagles are killed in collisions with their turbines. (Oil and power companies have been charged.)
In the future, the American Wind Wildlife Institute (AWWI) hopes to be able to provide better, more precise information about how birds and other wildlife interact with wind farms. For now, though, much of that data is spread out and under wraps.
That's why AWWI, a five-year-old alliance between 22 wind companies and nine conservation groups, has launched a new project to collect and analyze previously confidential surveys and studies prepared by wind farm operators across the country.
"Our goal is not to identify problems to prosecute," said Abby Arnold, AWWI's executive director. "Our goal is to develop a really good analytic tool that experts — biologists, statisticians, ecologists — and the wind industry can use to understand what these impacts are, where they're occurring, and how we can address them."
Confirmed eagle deaths at wind farms are extremely rare, but the numbers and public perception are skewed by one set of wind farms in California's Altamont Pass region, where an average of 67 golden eagles are killed annually. Outside of Altamont Pass, only around 50 golden eagles are known to have been killed anywhere else since the industry began.
The Associated Press story cited a March 2013 study published in the Wildlife Society Bulletin that said more than 573,000 birds are killed by wind turbines each year. The American Wind Energy Association maintains that the actual number is less than 200,000 birds annually.
Either way, the numbers are small compared to other known causes of bird fatalities.
According to the U.S. Fish & Wildlife Service, cars may kill 60 million birds or more each year. Building windows are to blame for more than 97 million bird deaths annually. Communication towers conservatively kill 4 to 5 million birds per year, and it could be ten times more. Power line fatalities could be "as high as 174 million deaths annually." Pesticides poison at least 72 million birds annually, and up to two million are killed each year in oil and wastewater pits.
One study found domestic cats kill 39 million birds annually in Wisconsin alone, with the national total likely hundreds of millions per year.
Most wind developers are required to conduct wildlife impact studies before and after projects are built. The results are typically seen by local regulators but never broadly disseminated beyond that, in part because wind companies worry opponents will use the results in anti-wind campaigns.
After a successful pilot project, AWWI has started collecting post-construction wildlife impact studies from its members, which include some of the nation's largest renewable developers. GE Energy, Horizon Wind, and Iberdrola Renewables are among the founding partners, along with the Audubon Society and the Association of Fish & Wildlife Agencies.
The American Wind Energy Association passed a resolution in support of the project two years ago, encouraging its members to participate. A big reason why wind companies may be embracing the project is that the data will be made anonymous before it's shared with researchers or the public.
Wind firms can go to a web portal to upload studies, but the information will be scrubbed of any references to specific wind farms or companies. What's left will include details about turbines, surrounding habitat, bird kill counts and survey methods.
Arnold said they hope to collect a critical mass of post-construction studies by the end of the year so that they can begin making it available to analysts next year to begin research with the data. The goal is to eventually have published, peer-reviewed research based on the database.
Among the questions that might be answered, according to Arnold: What is the avian fatality rate at wind farms? How does that rate vary by species? How do different fatality survey methods affect the results? And how do pre-construction estimates compare to post-construction data?
"We agree that these impacts are important," Arnold said, "and that's why the wind industry and conservation groups have formed this institute."