Federal wildlife officials announced Monday they have approved measures taken at Maryland's first industrial wind energy project to reduce the risk of spinning turbine blades killing endangered bats and birds.

Exelon Generation, which owns and operates the 28-turbine Criterion wind project built in 2010 in Garrett County, has pledged to "feather" or reduce the rotation speed of its turbines' blades during nighttime from late summer to early fall, peak bat migration time. The company also has agreed to install a protective gate over a bat cave in a neighboring state as mitigation for its turbines possibly killing one or more Indiana bats. The tiny, insect-eating bats are found, though rarely, across much of the eastern United States. Wildlife officials had predicted without feathering the turbine blades could kill as many as 28 of the federally protected bats over 20 years.

Exelon also has taken steps to reduce bird deaths at its Backbone Mountain project, once deemed to have one of the highest avian mortality rates of any wind farm in the country. Julie Slacum of the U.S. Fish and Wildlife Service said bird kills have come down dramatically by turning off lights on the turbines and outbuildings at night. The company further agreed to bury power lines, removing a potential obstacle for birds as they fly.