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Can Painting Wind Turbine Blades Black Really Save Birds?

A new study outlines a solution to the problem of wind turbine collisions. Experts say it’s promising, but they’re not sold just yet.

Wind turbine in the Smøla wind‐power plant with painted rotor blade. Photo: Roel May

The Smøla wind farm, located on an island off the northwestern coast of Norway, ran into a problem not long after it began operations in 2002. Or, to be more precise, the problem ran into the wind farm: White-tailed Eagles kept dying after flying into turbines, and nobody knew why they couldn’t see the blades. So Roel May, a researcher at the Norwegian Institute for Nature Research (NINA) in Trondheim, decided to find out. Beginning in 2006, May spent five years on a project called BirdWind, studying why birds collide with wind turbines and what happened when they did. Then, he turned his attention to the next step: how to stop birds from hitting the turbines in the first place.

If May and his colleagues could find a solution, the implications would be huge. Wind power is a growing part of the energy sector, both globally and in the United States. But turbines and birds have historically been at odds; according to the U.S. Fish and Wildlife Service, between 140,000 and 500,000 birds die in the United States alone after colliding with wind turbine blades each year.

One possible reason for these collisions is motion smear, which is the visual effect we experience when a fast-moving object appears blurry. It’s the same phenomenon that makes hummingbird wings nearly invisible to us when they’re in flight. We know intuitively that the wings aren’t actually a blur; they’re just moving too quickly for our eyes to process. Some researchers think birds experience the same effect when they see wind-turbine blades, only they don’t have the knowledge to understand it’s a moving object. “Neutrally painted blades are traveling fast enough that a bird has a hard time resolving them,” says Taber Allison, director of research at the American Wind Wildlife Institute, a nonprofit that brings together scientists and the wind industry to study and reduce wind energy’s impact on wildlife. The white or gray blades of a wind turbine in motion blend into the background against a light sky, and birds in flight don’t see them until it’s too late.

To address the problem, May and his colleagues at NINA looked to an old report from the U.S. National Energy Research Laboratory. It had never been formally peer-reviewed or published in a scientific journal, but offered a tantalizingly simple solution: Maybe, the report suggested, painting one of the turbine blades black could reduce motion smear. May and his colleagues decided to try it out, and the operators of the Smøla wind farm, who were co-funding their research, happily let them borrow a few turbines for the experiment. “The expectation,” wrote May in an email to Audubon, “is that this design reduces so-called motion smear, making the blades more visible to birds.”

Since the wind turbines were already up and running, May and his team had to hire a specialized team of painters who could rappel onto the turbine blades and paint them in midair. This drove up costs significantly, which meant they could paint the blades of only four turbines at Smøla. They decided to base their study on a total of eight turbines: four bearing a single black blade, and four unpainted turbines for comparison. Wind farm staff were already walking trained dogs through the area to search for bird carcasses, and this continued after the paint job. In all, the eight experimental turbines were monitored for more than 10 years—seven and a half years before and three and a half years after treatment—and were searched 1,275 times during that period.

The NINA team’s finished study, published in late July in the journal Ecology and Evolution, suggests that the solution might work. Bird deaths at Smøla, as measured by discovered carcasses, declined by 70 percent after the blades were painted. The theory goes that the black paint made the blades more visible, especially at the tips, essentially creating dark streaks in the sky that alerted incoming birds to the turbines and gave them time to change course.

The results are promising, says Garry George, director of Audubon’s Clean Energy Initiative, but they’re also preliminary. Eight turbines—half of which were treated with black paint—is not a large sample size, he says, and the researchers found relatively few bird carcasses both before and after painting the blades: A total of 42 dead birds, found at all eight turbines during the study period, were included in the analysis. It’s also not clear if the paint solution achieves the same results across various species of birds. May himself agrees: “Although we found a significant drop in bird collision rates, its efficacy may well be site- and species-specific,” he says. “It is surely not a golden egg solving all bird-collision problems in the world.” He recommended that more turbine operators test the approach around the world to see whether it works in different places and with different bird species.

If it does work, Allison says, painting blades black would be an effective, low-cost solution. But giving birds visual cues with paint isn’t the only solution researchers are testing. More thought is being put into siting, or figuring out where to physically place turbines. By studying nesting areas and common flight paths near potential wind farm locations, Allison says, wind companies can build turbines as far as possible from frequented bird routes. Additionally, wind farms are experimenting with radar, camera, and GPS tech to track birds and automatically shut off turbines as the birds approach. Still, since birds use wind to navigate and soar, there’s inevitably going to be some overlap between the best locations for wind farms and the best migratory pathways for birds.

Researchers are also experimenting with deterrence systems. “When you detect something that you think might be an eagle within a certain distance of a turbine, you emit sounds that will first alert the bird,” Allison says. “If the bird keeps coming, you send a second signal that—you know, the hope is it will persuade the bird to change its flight path.” The turbines will, in essence, scream at birds to stay away, and a report published by AWWI suggests this method could reduce collisions by somewhere between 33 and 53 percent.

Future research might prove that black turbine blades are the wind energy panacea we’ve been waiting for, but for now the idea of seeing painted blades dotted across the landscape is still up in the air in the United States. That’s because painted turbine blades are currently prohibited by Federal Aviation Administration (FAA) regulations, in part due to concern about reduced visibility for aircraft flying at night. “However, we do have a process for considering such changes,” an FAA spokesperson wrote in an email to Audubon—which sounds like they might consider changing their rules.

In the meantime, May says, researchers in South Africa and the Netherlands have expressed interest in replicating his study. He has also received a permanent exemption from regulations for his four turbines in Norway—so they will stay as they are, painting black streaks in the sky, hopefully saving a few more birds along the way.

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