Duke Energy Renewables, under federal investigation for the deaths of golden eagles at two Wyoming wind farms, has stepped up efforts to protect the birds, including the installation of a new radar system.
Duke Renewables spokeswoman Tammie McGee says the efforts appear to be paying off. Duke, which logs the death of each eagle found at its wind farms, has had no deaths at the two farms since September.
Duke owns a total of four wind farms in Wyoming. The largest, Top of the World in Converse County, has recorded 10 inadvertent deaths of eagles since it opened in 2010. It accounts for the most raptor deaths of Duke’s 14 farms scattered across six states.
Charlotte-based Duke Energy Corp. (NYSE:DUK) noted the investigation in its most recent financial filing last week with the Securities and Exchange Commission. The company says it is cooperating with the U.S. Department of Justice and the U.S. Fish and Wildlife Service in the investigation.
Federal officials say they cannot comment on the investigation because it is continuing.
The Associated Press published a story Tuesday on eagle deaths due to wind turbines. It estimates that eagles are killed about once a month in Converse County, Wyoming, where Duke has its Top of the World and Campbell Hill wind farms. It quotes an estimate published by the Wildlife Society Bulletin in March that calculates some 573,000 migratory birds are killed annually at U.S. wind farms. About 83,000 of those, the story says, are hunting birds such as hawks, eagles and falcons.
Campbell Hill, with 66 turbines, was built in 2009 on 13,000 acres in Converse and Natrona counties. There have been three eagles killed by turbines on that site since it opened. Top of the World, one of Duke’s largest wind farms, has 110 turbines on 17,000 acres.
McGee says Duke works to avoid the accidental killing of eagles and other migratory birds. That extends to stopping turbines in the path of any eagle seen flying into a farm’s airspace. Duke has trained its technicians at the projects to spot raptors.
The company also employs biologists to watch for birds at the sites. During the heavy migration season in winter and early spring, she says, Duke has two or three biologists – some on Duke’s staff and some hired by contract – working Top of the World and Campbell Hill daily, scanning the skies for eagles.
If eagles are spotted heading toward any turbines, she says, the spotter notifies the control room in Charlotte which operates the wind farms. She says a turbine can be shut down from there in as little as two minutes to protect eagles and other birds, stopping the blades immediately despite their enormous size.
“We curtail the operation of the turbines, sometimes at a significant costs,” she says.
The company also attempts to curtail turbine operations to accommodate eagle migrations patterns.
She says finding ways to limit accidental avian deaths has been a learning process. Duke Renewables continues to monitor migration patterns and eagle habits to avoid problems. The company attempts to keep the wind farms clear of dead animals that might attract scavenger birds.
Part of the problem is that the eagles are not watching for the wind turbines. They are scouring the ground for prey and will often fly straight into the rotating blades.
The radar system, originally developed for troops in Afghanistan to detect incoming missiles, was set up to monitor Top of the World in December. “We continue to test its effectiveness to detect individual eagles in proximity to our wind turbines,” she says.
She says Duke develops site-specific procedures for each wind farm it operates to reduce accidental deaths. And she says the company voluntarily reports all dead eagles found at its wind farms to Fish and Wildlife officials.
It has been more than eight months since an eagle has been found dead at either Top of the World or Campbell Hill, McGee says. “We believe our mitigation efforts are beginning to show results.”