A major US power company has pleaded guilty to killing eagles and other birds at two wind farms and agreed to pay $1 million as part of the first enforcement of laws protecting birds against wind energy facilities.

Until the settlement announced on Friday with Duke Energy and its renewable energy arm, no wind energy company had been prosecuted for a death of an eagle or other protected bird.

The company pleaded guilty to killing 14 eagles and 149 other birds at its Top of the World and Campbell Hill wind farms outside Casper, Wyoming.

The deaths, which included golden eagles, hawks, blackbirds, wrens and sparrows, occurred from 2009 to 2013.

“Wind energy is not green if it is killing hundreds of thousands of birds,” said George Fenwick, president of the American Bird Conservancy, which supports properly sited wind farms.

Wind farms are clusters of turbines as tall as 30-storey buildings, with spinning rotors as wide as a passenger jet’s wingspan.

The blades can reach speeds up to 270km/h at the tips, creating tornado-like vortexes.

Eagles are especially vulnerable because they don’t look up as they scan the ground for food, failing to notice the blades until it’s too late.

“No form of energy generation, or human activity for that matter, is completely free of impacts, and wind energy is no exception,” the American Wind Energy Association said in a statement.

The case against Duke Energy and Duke Energy Renewables was the first prosecuted under the Migratory Bird Treaty Act against a wind energy company.

The Obama administration has used the law against oil companies and power companies for drowning and electrocuting birds.

Once a wind farm is built, there is little a company can do to stop the deaths.

As part of the agreement, Duke will continue to use field biologists to shut down turbines when eagles get too close.

It will install radar technology similar to what is used in Afghanistan to track missiles. And it will continue to report all bird deaths to the government.