WASHINGTON (AP) -- Wind farms are seen as a boon to the environment, but scientists are expressing worries the large towers could harm wildlife.
Wind farms generate electricity by using the wind to turn giant blades that rotate turbines to make power.
In a study requested by Congress, scientists say the threat the spinning blades pose to birds and bats needs further study. The birds at most risk appear to be night-migrating songbirds, bats and some hunting birds.
But the risk is not well enough known to draw conclusions.
Wind farms now operate in 36 states. Scientists estimate wind farms could generate as much as seven percent of U-S electricity in 15 years.