Painting One Wind Turbine Blade Black Cuts Bird Deaths By 70 Percent

Painting a single blade black on a wind turbine reduced bird deaths at a Norwegian wind farm by more than 70 percent, according to a study published in the journal Ecology and Evolution. The findings came from years of fatality tracking at the Smøla wind power plant off Norway's coast.

Researchers from the Norwegian Institute for Nature Research, led by Roel May, tested whether painting one of a turbine's three rotor blades black would reduce collisions, building on earlier laboratory work suggesting the change could reduce what scientists call motion smear.

Motion smear occurs because blade tips can travel up to 250 kilometres an hour, a speed at which the moving blade effectively blurs into invisibility for birds attempting to judge its position and avoid it.

The team painted one blade black on four turbines and compared bird deaths there with fatality rates at unpainted, neighbouring turbines used as a control group. They tracked mortality for roughly seven and a half years before painting and three and a half years after.

The annual fatality rate at painted turbines fell by over 70 percent compared with the unpainted controls. The effect was strongest among birds of prey, with no white-tailed eagle carcasses recorded at the painted turbines after the change was made.

Because the Smøla turbines were already operational when the study began, workers had to paint the blades while they remained mounted in place rather than during manufacturing or installation.

The result has since drawn interest from wind operators elsewhere. Energy company PacifiCorp launched a larger trial painting individual blades across 36 turbines at its Glenrock wind farm in Wyoming, running since 2023 to test whether the Norwegian findings hold up in a different environment and among different bird species.

Researchers have cautioned that the original Smøla study involved a relatively small sample of just four painted turbines and four controls, meaning wider trials are needed before the approach can be considered a proven, large-scale mitigation measure for bird collisions at wind farms.