A Life-Saving Coat Of Paint: Birds, Wind Turbines, And Visual Cues

Seeing an obstacle ahead may seem trivial to humans, because our sense of sight faces forward and combines input from both eyes, giving us a fairly precise sense of objects standing in our way. Birds, on the other hand, have evolved different visual capacities. Their eyes are better at detecting threats, prey, and other members of their own species using lateral fields of vision. 

Because of this, birds living in and around wind farms may not detect wind turbines in time to avoid them as they fly. This has resulted in increasing numbers of injuries and deaths among various avian species as more and more wind farms are being built. If unresolved, this could lead to an impasse between the need for clean energy generation and the protection of wildlife. This study set out to identify a practical and cost-effective measure to lessen rates of collision suffered by bird populations on wind farms, at least among some bird species: painting a turbine blade black.

From the outset, the authors note that other techniques aiming to reduce collisions between birds and wind turbines do exist. The research paper cites two primary methods: a seasonal shutdown when birds are expected to fly through a wind farm on their migration route, and the ploughing of the surrounding soil. However, these solutions are either expensive in terms of productivity losses, or labour-intensive, both of which undermine the viability of investing in wind farms. More “passive” approaches are therefore desirable. 

Wind turbines are typically painted white, and by presenting little contrast against the sky, the operation of wind turbines creates motion blur. This makes it difficult for birds to detect and avoid blades as they fly near them. May’s team tested a hypothesis suggesting that, based on how avian sight works, increasing visual contrast by painting blades black would render turbines more visible to birds. They carried out their research in a Norwegian archipelago featuring a sizable wind farm, which provided a good sample size. The archipelago is also recognized as a busy haven for various bird species. 

A substantial amount of data on bird fatalities due to collisions with turbines at this site, covering several years before the study began, was available. This enabled the team to use data from before, as well as during, the study. Analysis of these data yielded evidence-based conclusions spanning a total of 10 years. Accordingly, May’s team chose a “before-after-control-impact” approach, comparing bird fatalities around the painted wind turbines firstly with the amount of deadly collisions over the years before they were painted, and secondly with nearby control turbines, i.e. turbines that were not painted. To enable an accurate interpretation of the dynamics at play, the team recorded the species involved in each bird/turbine collision. Indeed, different bird species face different challenges due to their individual sensory and motion capacities. Willow ptarmigans, in particular, are known to collide with turbine bases rather than blades. Improvement in casualties among this species was therefore not anticipated under this experiment. 

The results were remarkable: simply painting one blade black on a set of wind turbines led to a 71.9% average drop in fatalities in their respective vicinity compared to the annual rate around unpainted turbines surrounding the painted ones. Results reveal the clearest improvement for raptor species — namely, in the local ecosystem, white-tailed eagles. 

The researchers identified some issues to consider and areas requiring additional research. Firstly, the painting of rotor blades had to be carried out without disassembling the turbine tower, which made it a significant task. Of course, painting one of the blades of each newly-made turbine was much simpler than painting them once they are mounted on a tower, which suggested that this approach could be rolled out in new wind turbine production smoothly and at very low cost — it simply makes it harder to ensure that existing wind farms undergo this treatment to protect wildlife. 

A second point they raised was that this study was only carried out at one site, and additional research at other sites would help to ensure similar results can be expected across a variety of wind farm environments and ecosystems. This is especially true because within the study, results varied markedly from one year to the next, although the cause for the variation is unknown. The team also encouraged more research on whether other colors than black would be as effective.

Thirdly, the paper recognized that some bird species may not be significantly helped by this approach, for instance because they typically collide with towers rather than blades, which means painting a blade is likely insufficient as a single measure. 

Human activity has long interfered with the safety and welfare of wildlife. As our technological capabilities have increased, however, they’ve led us to build systems affecting more and more areas that have until now been relatively safe sites for wildlife. Even though these systems may hold the promise of lower environmental destruction with respect to climate change, we need to take their secondary effects seriously. Research on ways to mitigate our impact on wildlife can therefore be highly beneficial, especially when simple changes can have a significant impact on non-human lives.