Songbirds until recently were the most frequently reported fatalities at U.S. utility-scale wind facilities, The Journal of Wildlife Management reported in a news release. Another study showed 78 percent of carcasses found at wind-energy facilities outside of California were songbirds, about half nocturnal, protected by the Migratory Bird Treaty Act.

Recent monitoring studies indicate that energy utility-scale, wind facilities killed more bats than were expected based on earlier studies, reported the Journal, published by The Wildlife Society in Bethesda, Md. Reports indicate large numbers of bats have been killed at facilities along forested ridge tops in the eastern United States.

States are inconsistent on surveying the effects of turbines have on local environments, researchers said.

Researchers recommended several methods to study impacts of wind-energy facility on nocturnal birds and bats, including moon-watching, tracking radar, audio microphones for birds and ultrasound microphones for bats.