PITTSBURGH -- Wind turbines in Pennsylvania kill an estimated 10,500 bats and 1,680 birds each year, according to a report from the Pennsylvania Game Commission.
That's an average of 25 bats and four birds at each of the state's 420 turbines.
The Daily American of Somerset reported that approximately 30 participating developers agreed to conduct one year of pre-construction and two years of post-construction monitoring of birds and bats at each site using Game Commission data-collection and study guidelines.
The report found no eagle deaths and three endangered bird deaths. The birds (all found in September 2009) included two blackpoll warblers and one yellow-bellied flycatcher. All three were considered to be migrants. Two endangered Seminole bats carcasses were also found during the study, and were also believed to be migrating.
State wildlife biologists aren't sure how the deaths will impact the long-term health of bat and bird populations.
"We don't really have a good population estimate on bats, so 25 bats per turbine per year seems like a lot, and if you do the math with all of the turbines we have -- and how many are proposed -- it's a huge number," said Tracey Librandi Mumma, a supervisory wildlife biologist for the commission. "But whether that number will impact the population is something we're wrestling with right now."
Experts said the impacts could vary greatly by species.
With some endangered species the loss of a single bird could be detrimental, while with common species the loss of several hundred birds wouldn't have a major impact, Paul Fischbeck, a professor of engineering and public policy at Carnegie Mellon University, said Wednesday.
Michael Gannon, a professor of biology at the Pennsylvania State University of Altoona and a recognized bat expert, had reservations about the report.
"One of my chief concerns is that they're keeping their (raw) data very secret. Does the data support their conclusions? If you can't review something it's not science," Gannon told the Daily American.
The report noted that some wind sites in Pennsylvania were not part of the cooperative study. Florida Light & Power Energy's subsidiary, NextEra Energy Resources, has five active projects and is the largest non-cooperating developer.
The report said that 31 of the 86 projects have a high risk of bat mortality, and 15 have a high risk of bird mortality. The Nature Conservancy estimates that between 750 and 2,900 additional wind turbines may be built in Pennsylvania by 2030.
Fischbeck added that just focusing on deaths caused by wind turbines doesn't tell the whole story. Another recent scientific study found that cats caused more deaths in a suburban area than any other predator.
A U.S. Department of Agriculture report estimated that about 550 million birds are killed each year in collisions with buildings, 130 million in collisions with power lines, 100 million by cats, 80 million by cars, and 67 million by pesticides. Wind turbines kill about 28,500, or far less than 1 percent, the report said.