By Bruce Schreiner CHARLESTON, W.Va. -- The operator of a southern West Virginia wind farm estimates that several dozen endangered bats could be killed by flying into turbine blades during a 25-year period, according to a federal review of the risks to the flying mammals.The estimated death toll comes as Beech Ridge Energy requests a permit under the federal Endangered Species Act that would allow the "incidental take," or killing, of endangered bats that collide with the turbines.The law, however, requires permit applicants to meet a certain threshold for minimizing damage to endangered wildlife.So far, Beech Ridge reports it hasn't found any dead Virginia big-eared or Indiana bats at its wind farm, consisting of 67 turbines with up to 33 more planned in Greenbrier and Nicholas counties.Even with efforts to minimize risk to bats, the U.S. Fish and Wildlife Service says some deaths are possible.Beech Ridge estimates that the death toll could reach 53 Indiana bats and 14 Virginia big-eared bats over a quarter century, the service said. That reflects a lower estimated mortality rate among Indiana bats. Beech Ridge earlier predicted that as many as 70 Indiana bats could be killed."This lower take is based on the company's commitment to further reduce take, as well as on recent data on bat species abundance and composition in the landscape," the Fish and Wildlife Service said.The Endangered Species Act makes it illegal to harm or kill federally threatened or endangered wildlife.The review process is entering its last stages. Final versions of the company's habitat conservation plan and the Fish and Wildlife Service's environmental impact statement were released for public scrutiny in recent days.A decision on whether to approve the incidental take permit could come by year's end.Beech Ridge would make annual reports on bat deaths at the wind farm, about 20 miles northwest of Lewisburg.Energy companies can reduce the risk to bats by modifying wind farm operations when the animals are most active, the wildlife agency said.Beech Ridge's wind farm operates year-round. However, the company has limited operations when bats are most active.During nighttime from spring to autumn, the turbines operate only when wind speeds exceed 15.43 mph. When wind speeds are lower, the blades are positioned so only minimal rotation occurs.Beech Ridge says it is proposing other operational steps to try to keep bats from flying into turbine blades.The wildlife agency said such efforts can reduce bat deaths "with relatively small losses of power generation."Also, Beech Ridge is pursuing off-site projects aimed at protecting Virginia big-eared and Indiana bat populations.One project will try to safeguard Indiana bat hibernating, swarming and foraging habitat. The company also plans a cave-gating project to protect hibernating Virginia big-eared bats.The Indiana bat has been on the federal endangered species list since 1967. The bats are found over most of the eastern U.S., and their 2013 population across 17 states was estimated at 532,846, down 4 percent from 2011.Indiana bat populations have been hit by white-nose syndrome. The disease prompts bats to wake from their winter hibernation and die when they fly into the winter landscape in a futile search for food.The Virginia big-eared bat has been listed as endangered since 1979. Its population has increased from 1,300 to more than 13,000 since then in Virginia, West Virginia, Kentucky and North Carolina.Beech Ridge is seeking the permit to comply with terms of a lawsuit settlement.The Washington, D.C.-based Animal Welfare Institute and the Williamsburg, W.Va.-based Mountain Communities for Responsible Energy had sued both Beech Ridge Energy and its parent, Chicago-based Invenergy LLC, in 2009.Beech Ridge built 40 turbines before a federal judge in Maryland ruled that it had failed to obtain the necessary permit.The West Virginia Public Service Commission approved the wind farm in 2006, but it took a state Supreme Court ruling to clear the way for construction. Local residents had also sued, claiming the project would harm property values and views.