Sen. John Thune, R-S.D., has written U.S. Fish and Wildlife Service officials to say that changing wind farm policies based on the chance that migrating whooping cranes might be hurt would send a bad message.

Thune asked the agency not to overreact to a study that says whooping cranes migrate along the Missouri River. Protecting the cranes' habitat is not a reasonable excuse for blocking wind energy production, he said.

"The suggestion that more wind energy production would impair the wildlife population, we think is suspect, so we're challenging that assertion," Thune said.

Leroy Ratzlaff of Highmore, on whose land wind turbines are being built, said he has yet to find a dead bird beneath any of the turbines.

The American Wind Energy Association says modern wind turbines are less harmful to waterfowl than existing objects such as airplanes, tall buildings, vehicles and radio towers.