WASHINGTON - Jessica Kerns thought her survey of new power-generating wind turbines on a mountaintop in West Virginia would yield the standard result: a smattering of dead birds that were whacked by the whirring blades.

But the University of Maryland doctoral student turned up something unexpected amid the trees and rolling ridges of Backbone Mountain: hundreds of bat carcasses, some with battered wings and bloodied faces. "It was really a shock," Kerns said.

Thousands of bats have died at Backbone and on another nearby wind farm in Meyersdale, Pa. -more per turbine than at any other wind facility in the world, according to researchers' estimates. The deaths are raising concerns about the impact of hundreds more turbines planned in the East, including some in western Maryland, as the wind industry steps up expansion beyond its traditional areas in the West and Great Plains.

The bat deaths, which have baffled researchers, pose a problem for an industry that sells itself as an environmentally friendly alternative to conventional power plants. Wind proponents already have had to battle complaints about bird deaths from the blades and about unsightly turbines marring pristine views.

The white turbines in Appalachia rise more than 340 feet above the ground - well above the tree canopy - and are lined up close to one another to catch the wind as it blows over the mountains and ridges.

The bat problem could worsen, conservationists fear, as wind developers rush to erect new turbines following the recent renewal of a federal tax break for a year. The wind industry, which had been virtually dormant since the last tax break expired a year ago, projects more wind turbines to be built around the country this year than in any previous year. In the areas near where bats have been killed in Pennsylvania and West Virginia, activists said, roughly 700 new turbines have been proposed or approved.

"Take the most conservative estimates of mortality and multiply them out by the number of turbines planned and you get very large, probably unsustainable kill rates,"said Merlin Tuttle, president and founder of Bat Conservation International, whose Austin, Texas-based group is leading the research effort in Appalachia. "One year from now we could have a gigantic problem."

Bats serve an important role in nature, and their populations are believed to be in decline, scientists said. The bats getting killed in Appalachia devour insects that pose grave threats to crops such as corn and cotton. They also feast on pests that can spread disease, such as mosquitoes.

On Backbone Mountain, at a facility called Mountaineer Wind Energy Center, the first dead bats were found in 2003, soon after the project's 44 turbines came online. Conservationists and the wind industry hoped the deaths were a fluke.

But Kerns and other researchers returned last year and now estimate the 2004 death toll at between 1,500 and 4,000 bats. Nearby, another group of researchers, working at the 20-turbine wind farm in Pennsylvania, which came online a year ago, found a raft of bat carcasses as well.

Researchers do not know why bats are flying into the turbines. Armed with radar and thermal imaging cameras, they are trying to come up with recommendations for wind power developers to avoid the problem. Researchers are uncertain whether bats are attracted to the spinning blades or if their sonar, which allows them to find food and avoid trees and other objects, fails to detect the turbines.

None of the species of bats found on the two mountains is endangered, said Albert M. Manville II, a biologist with the U.S. Fish and Wildlife Service. The carcasses found include those of hoary, red and eastern pipistrelle bats. The deaths appear to violate no federal laws, Manville said, but the threat is serious. Unless a solution is found, he said, the turbines could get a reputation as being "bat Veg-o-matics."

The large number of dead bats caught the wind power industry by surprise, and now its leaders are scrambling to find a solution.

"It was something that when we found out about it we felt we needed to respond to immediately," said Laurie Jodziewicz of the American Wind Energy Association in Washington, which also is participating in the research. "What we wanted to do this year was to get a handle on what's going on. "

The wind industry confronted its biggest environmental challenge when early model turbines in Northern California killed large numbers of birds. The industry says newer turbines and more attention to site selection have dramatically cut the number of bird deaths in subsequent projects around the country, though some environmentalists say too many birds are still dying.

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