This ‘acoustic lighthouse’ could keep birds from killing themselves on wind turbines
Clean energy doesn't have to be deadly.
Secretary of the Interior Ryan Zinke recently falsely claimed that wind turbines kill 750,000 birds each year. In actuality, wind turbines kill a little more than 350,000 birds annually — which is far fewer than cars, house cats, or plate-glass windows put to death. What’s the biggest threat to our flying friends? According to the Audubon Society, it’s climate change.
Of course, to draw down heat-trapping carbon pollution, we need to ramp up wind power by an order of magnitude, which will put a lot more birds in danger. Fortunately, it seems scientists have found a fix. Researchers at the College of William & Mary have built an innovative device that alerts birds in danger of crashing into a wind turbine.
“There’s a lot of interest in developing near-shore or offshore wind energy. Putting large, rotating structures that look like mincemeat-makers in the sky isn’t going to be good for the birds,” said biologist John Swaddle, at the annual meeting of the American Association for the Advancement of Science. Swaddle wants to equip turbines with his new invention, the Acoustic Lighthouse, which warns bird to look up before it’s too late.
Birds, which have eyes on the sides of their heads, look down and to the side when horizontal. That means that, when flying, their eyes are on the ground, which helps them navigate. For most of their evolutionary history, this didn’t pose a problem. Soaring several hundred feet above the ground, birds were unlikely to run into a tree.
Today, however, human-made structures like skyscrapers, cell phone towers, and wind turbines reach into the sky, creating unseen obstacles for birds in flight. When a downward-looking bird runs headfirst into a wind turbine, it dies almost instantly.
“That risk is not evenly spread across the world. It’s concentrated in certain areas, because wind is concentrated in certain areas,” Swaddle said. “That’s where the wind turbines are — and that’s where bird movement is sometimes concentrated, especially during migration.”
The Acoustic Lighthouse generates a high-pitched sound that prompts birds to slow down. Birds hit the brakes by pointing their tail feathers down, which makes their body shift upright, causing them look ahead instead of at the ground. “All that’s missing is the brake-screeching sound,” Swaddle said.
If a birds looks up and sees a wind turbine, it will change course and fly around the obstacle. If it doesn’t look up until the last second, simply making its body vertical might spare it from a fatal brain injury. “It’s a bit like someone texting while they’re driving,” he added. “If you honk your horn at them, they’ll look up.”
Swaddle, along with former William & Mary graduate student Nicole Ingrassia, tested the technology with captive zebra finches. The birds flew down a long corridor toward a mesh net. The Acoustic Lighthouse got some birds to look up in time to avoid the net, and it prompted many others to slow down substantially. The researchers published their findings in the journal Integrative and Comparative Biology.
Swaddle is now looking to scale up his invention. “If you want to apply this to a building or to a wind turbine, that kind of free-flying situation, you’d project the sound field 50 or maybe 100 meters in front,” he said. “So when a bird enters that zone, it gets plenty of warning.” He explained that, because the speaker is directional, and it would be mounted atop a very tall wind turbine, people on the ground would be oblivious to any sound.
The Acoustic Lighthouse could resolve a central conflict around wind energy. Some conservationists oppose wind energy because turbines post a threat to birds. By equipping turbines with a warning system, power utilities might assuage the concerns of bird lovers.
“There’s been some situations in which a single eagle has hit a wind turbine and the penalties associated with that have shut down that wind farm for weeks on end,” Swaddle said. “We’re not going to stop using electricity, and so we need to find ways to live with wildlife more sustainably.”