top of page

A Biologist Works to Reconcile Bats and Wind Energy



Tim Hayes’s early interactions with bats on his grandparents’ Indiana farm didn’t scream “future bat expert.” He recalls sitting outside with his brother at dusk watching them flutter out of the barn and throwing a sock filled with pebbles in their direction. “We were kids,” he says. “The bats would chase the sock.”

Now the 52-year-old biologist (and bat expert) runs the environmental program at Duke Energy Renewables, the wind-and-solar division of power giant Duke Energy. His fascination with bats took on a professional urgency several years ago when researchers found that swarms of migrating bats were flying headlong into wind turbines across the Eastern U.S., dying by the thousands. Scientists are trying to figure out exactly why. Some theorize bats are attracted to the turbines’ height, mistaking them for tall trees, or that the moving blades confuse the bats’ biological sonar.

Bats are nocturnal and navigate in the dark using echolocation—a series of high-pitched chirps. They manage to hunt insects and avoid power lines, yet fail to interpret the danger of fast-spinning blades on a 300-foot turbine. A 2013 study from the University of Colorado estimated that wind turbines kill as many as 600,000 bats a year. Some of those fatalities include threatened species.

On wind farms in Western states such as Wyoming, the focus is on preventing bird strikes—mainly by Golden Eagles.

Mr. Hayes and other biologists in the wind-power industry are developing methods for minimizing bat and bird fatalities. He estimates he spends about 40% of his time on the road, visiting Duke Energy’s 18 wind sites across the country or attending conferences. His team is working with organizations including Bat Conservation International and Bats and Wind Energy Cooperative testing acoustic deterrents, idling turbines at night during the fall migration season, and adjusting the angle of the turbine blades, called feathering.

“I have a soft spot in my heart for bats. People think they’re creepy and have rabies and are vampires and whatnot, and they just don’t get the credit they deserve,” Mr. Hayes says. “I cannot think of another mammal that does more for people in terms of pest control and pollinating plants.”

Indeed, as concerns escalate about mosquito-borne illnesses like the Zika virus, bat specialists point out that one bat can consume as many as 1,000 mosquitoes in an hour, according to the U.S. Forest Service. A bat colony can wipe out tens of thousands of mosquitoes in a night. They also prey on insects that feed on crops, saving the U.S. agriculture industry at least $3 billion a year in pesticide costs, according to a 2011 Boston University study.

Mr. Hayes packs most of his equipment in a canvas backpack, including a pair of Swarovski binoculars, a spotting scope and a headlamp. Much of his field work takes place at dusk. He treasures his Thermacell insect repellent device, which emits a vapor that creates a bug-free zone of about 15 square feet. “It’s a lifesaver if you’re doing field work in a mosquito-prone area which, if you’re a bat person, you are,” he says.

His snakebite kit remains unopened despite years in the field, but he packs it anyway, along with snake chaps, which are leggings made of Kevlar.

His job includes scouting potential wind and solar sites, which means hours of observing a landscape for habitat clues, he says. He carries Munsell Soil Color Charts to help determine if soil underfoot qualifies as wetlands, the local edition of the Peterson Field Guide for wildlife, a Rite in the Rain waterproof notebook and plenty of maps. “You’re often in places that don’t have good cell coverage,” he says.

Duke Energy tries to avoid placing wind projects on native grasslands, wetlands and unspoiled natural habitats, preferring sites with established human activity like farmland, ranch land or oil and gas development, he says. When doing a bat survey for a new wind-project site, he will bring rubber gloves, fine mesh netting and tiny radio transmitters for tagging.

“If you catch a lactating female, that’s the Holy Grail,” Mr. Hayes says. Among migrating bats, he explains, new mothers and pregnant females roost together, separate from the rest of the colony. Mr. Hayes needs to identify those “maternity roost trees” before construction begins so crews can avoid them until migration season is over.

Preventing eagle deaths takes vigilance. At one of its sites in Wyoming, where 110 wind turbines are spread over 26 square miles, Duke Energy has seven full-time biologists scanning the skies for raptors, he says. A technician in a control tower can regulate each turbine with the touch of a button. As soon as an eagle is spotted in the vicinity, the biologist radios the technician to slow down the rotor of the nearest turbine.

Mr. Hayes’s teams in Wyoming are currently being run ragged by another small furry animal: rabbits, which had a population explosion this spring. “We’re being invaded by rabbits, and you’re managing for Golden Eagles, who love eating rabbits,” he says. “It’s a challenge.”

bottom of page