For the birds

Experiment at the Smøla wind farm shows
promise in reducing avian fatalities

Photo: Stian LysbergSolum / NTB scanpix
Sea eagles are among the birds at danger from wind turbines.

ERIC STAVNEY
Mukilteo, Wash.

Researchers at the Norwegian Institute for Nature Research have found a simple way to reduce bird fatalities at a wind turbine farm. In a study published in Ecology and Evolution in July 2020, Roel May, et al. set up an experiment at Smøla wind-power plant located on an island west of about 70 miles west of Trondheim. 

Bird strikes are not uncommon in wind farms, and the frequency of deaths varies by the location of the farm and the kinds of birds flying through. So for the wind-power industry, which positions itself as ecologically friendly, reducing the impact on wild populations is especially important.

Previous studies of bird strikes have suggested that birds have trouble seeing the blur of whirling propellers as white-tailed eagle strikes, followed by a lesser number of willow ptarmigans and common snipes. Some of this makes sense, but some is counterintuitive.

The ptarmigan deaths can perhaps be explained by their limited forward vision. Ptarmigans have their eyes located more around the sides of their heads, so they have a blind spot straight ahead of them when flying. But they also don’t usually fly very high or very far. Most of the dead ptarmigans at the Smøla Wind Farm were found at the base of the turbine towers, with intact carcasses, suggesting that lacking good forward vision, they may fly straight into the turbine towers.

But the white-tailed eagles struck by the turbine blades are harder to explain. Some deaths were expected because of the large population of eagles on Smøla. Eagles, however, have excellent binocular forward vision, and theoretically should be able to see the whirling blades better than other birds. It could be that eagles may spend more time searching the ground for prey than watching where they’re flying. 

Photo: Kjell Herskedal / NTB scanpix
There are 68 wind turbines at the Smøla plant, about 70 miles west of Trondheim.

The experiment went like this: first, bird carcasses were collected around the 68 Smøla wind turbines, and identified by species, as part of regular maintenance activities for seven years. 

Then the researchers began their study by painting one of the propeller blades black on each of four turbines scattered through two different rows on the farm. Then scientists counted bird carcasses around those four and four other “control” turbines for four years.

Scientists hypothesized that while the whirling white turbine blades are hard to see, if one were black, the whole propeller would stand out better when turning. Painting one blade, rather than all blades, creates a stronger difference in the whirl of blades. 

The study found that white-tailed eagle fatalities dropped by over 70% around the turbines that were painted, while those around other turbines remained about the same as before.

This would seem to be a strong recommendation to the wind farm industry to paint propeller blades. But painting a blade on the wind farm required workers to use a lift to reach the blades, and only do it in calm weather. The researchers point to how much easier and cheaper it would be if one blade was painted before propellers are installed when wind farms are being built. 

Painting one blade didn’t seem to affect the ptarmigans much, however, as they continued to fly into the towers. A different solution, such as alternating stripes on the towers, might work for them.

The scientists concluded that while bird fatalities were greatly reduced in this experiment, the study was performed at only one wind farm in Norway, and involved a relatively small number of bird species common to that area. More studies are needed to see if this may be a dependable way to reduce bird fatalities at wind farms in other areas and with other bird populations. 

Jethro Gauld, a biologist from the University of East Anglia in Norwich, England, who was not involved in this research, would like to see similar studies done in southern Spain, where many wind farms overlap with the migratory flight paths of millions of birds. 

This article originally appeared in the Feb. 12, 2021, issue of The Norwegian American.