Birds are not being harmed by turbines though some bat populations are being affected, the Pennsylvania Game Commission and wind-energy companies indicate in their first annual report.

It’s too soon to draw any conclusions, said Tracey Librandi Mumma, a state wildlife biologist and wind energy project coordinator who worked on the study.

“All we have is the one study,’’ Mumma said from Harrisburg. “I don’t feel comfortable about making any generalizations. This is only one year’s worth of data from one (wind farm) site.’’

The Pennsylvania Game Commission Wind Energy Voluntary Cooperation Agreement First Annual Report was released recently.

Among the 20 wind power companies taking part is Gamesa Energy USA, which has a turbine plant in Ebensburg.

A confidentiality clause the state has with the wind companies prevented Mumma from saying where the data were collected. If the one-site study was conducted in a migratory bird lane, for instance, its finding that birds were not harmed would be noteworthy.

But the bat information, Mumma said, may be significant.

“Oh my gosh, migratory bats are being killed in great numbers,” Mumma said, recalling her initial reaction.

Mumma said trying to gauge windmill impact on overall bat populations is difficult. That’s because she doesn’t know how many bats are out there to begin with.

So experts don’t know, for instance, if losing three bats per month per turbine – a reasonable inference, then multiplied by hundreds of turbines on the Eastern Seaboard – is or is not significant bat loss. More research is needed, they say.

“It’s a big concern,” Mumma said. “We don’t know their populations but yet we’re putting up turbines up and down the East Coast.’’

No bats species listed as “threatened” – the Indiana and the small-footed bats – have been found on the ground near the turbines.

“They’re killing migratory tree bats,’’ Mumma said.

Some limitations

Veterinarian Dr. Jeffrey Payne of Berlin is skeptical of large-scale wind farms and fears they will have a detrimental impact on wildlife and habitat.

And while he appreciates that studies are being done, he’s not satisfied that they are reporting the full depth of the situation.

“When you talk about confidentiality in the studies, well, science has to be peer-reviewable,” he said. “Who is doing the studies? Is a bias being introduced?

“That has been kind of bothersome: If the wind companies have hired people to collect the information, it’s in their interest to not find stuff.’’

He said the cumulative impact of erecting thousands of towers – not just a few dozen here, a few dozen there – is what is really worrisome.

Mumma said the state is making the best decisions possible considering the limits of its authority. Unless threatened or endangered species are being willfully killed, there’s little her agency can do.

“If we didn’t (give confidentiality), no one would have signed the agreement and we wouldn’t have any data,” she said. “Yes, it’s got its faults from that peer-review perspective.’’

But, she said, if the voluntary agreements were not in place, the state would have much less information. And, she said, the Game Commission is taking a harder stance against the companies that are not cooperating in the study and not taking steps to minimize the impact on wildlife.

The data are being collected to give biologists enough information to make an educated guess as to what’s going on in the field, Mumma said.

Dead tree lookalike

Scientists believe that bats are attracted to turbines.

“One of the things we’re finding is more males are being killed than females,’’ Mumma said. “Males go to the highest structure to roost. In the dark, turbines kind of look like a dead tree.’’

Another consideration, Mumma said, is that, once they’re above the treeline, the bats may turn off “the GPS in their mind.’’

That’s because they’ve never come across anything bigger than a tree, she said. So why would they find anything to fear so high in the sky? Then they get whacked by a whirling blade.

Blade speed at the tip is deceptively high, Mumma said.

Payne and Mumma do agree on one thing: The value of bats.

“A lot of people say, ‘What’s a bat? It’s something you chase out of your house,’ ’’ said Payne, a birder and member of the Audubon Society. “But look at the bugs they eat. Whether the mosquitoes that bite us or eating pests in the fields, we’d have to use more insecticide.’’

And, said Mumma, the wildlife biologist, bats help pollinate plants.

“It’s scary to know with all this wind development we’re knocking out all these bats,” Mumma said. “It could have huge implications to the ecosystem. We know less of bats than we do of birds.’’

Payne takes the threat a step farther.

“You’re industrializing the habitat,’’ he said. “It’s not only the direct kills.’’

He said he finds birds breeding on Pennsylvania ridgetops that don’t breed any other place. He said those species need continuous access to woods.

The study did not find any kills of threatened or endangered birds.

Finding solutions

The bright news among all this bat mortality is that the answers are within reach.

For one, the early information is that most of the bat kills are taking place in the four months from June through September.

This means turbine use could be curtailed around dusk and dawn – when bats generally fly – during these months.

Mumma said the state wants to work with the wind companies to keep the window of turbine “down time’’ as narrow as possible.

“We don’t want to cost developers unnecessarily,’’ she said.

Also, operators might agree not to allow the turbines to spin during certain periods unless wind speeds reach a specific velocity.

That’s because bats don’t fly when the wind is up which – as fate would have it – is when the companies can generate the most power.

“At least one developer has experimented with changing turbine cut-in speeds during specific high-risk periods,” the study said. “Results of this have not yet been published.’’

Science is attacking the situation from the bat’s point of view.

Mumma said signals are being tested in the lab that would repel the flying critters.

The problem, she said, is broadcasting the signals – which only bats can hear – with enough energy to reach the tips of the blades. Putting the gear on the blades themselves would complicate the aerodynamics of the turbines.

Not building on sensitive sites is another way to minimize environmental harm.

“The environmental review does not currently consider migratory bird or bat pathways,’’ although that could change, Mumma said.

The study says three proposed project sites were voluntarily abandoned but, under the confidentiality rules, those locations were not released.

Carl G. Roe, Game Commission executive director, said the annual report will enable the commission and wind companies to make more informed decisions about where to locate wind farms as well as how to reduce wildlife mortality.