Black blade to reduce bird collisions

One method to prevent birds from becoming victims of collisions with a wind turbine is to increase the visibility of the rotating rotor blades by reducing motion blur. Laboratory experiments by Hodos (2003) showed that the occurrence of motion blur can be limited by painting one of the blades a different color. This principle was investigated by May et al. (2020) on the island of Smøla in Norway. That study investigated whether painting one blade of a wind turbine black resulted in a reduction in the number of collision victims. The results were very proming: applying this measure resulted in 70% fewer bird victims (May et al., 2020).

To determine whether this approach is also effective in the Netherlands, a research project was started at Windpark Eemshaven in 2021. At this Dutch coastal site, the species composition and landscape differ from the Norway study, and bird migration plays an important role in bird mortality at the wind turbines. The research was conducted at 14 existing RWE wind turbines at Windpark Eemshaven. After an initial year of victim research (baseline measurement), seven wind turbines had one blade painted black in September 2022. Victim monitoring was conducted for the two following years among all 14 wind turbines (effect measurement).

The study examined whether there was a difference in bird mortality between turbines with a black-painted blade and control turbines. This was compared to the differences observed between these groups of turbines during the baseline measurement. Contrary to what was hoped, the analyses did not reveal a significant effect of the black blade in the Eemshaven. In other words, we observed no reduction in the number of bird fatalities under the turbines with a black blade. This applied to both the total numbers of birds and to the various species groups studied. Additional research (project ZWEMT; video at the bottom of this page) into the flight behaviour near the turbines also demonstrated no differences in avoidance between turbines with or without blad blade.

It is unclear why a black blade led to a reduction in mortality in the Norwegian study, but not in the Eemshaven. This may be due to the relatively busy background of this industrial area: many different colors and objects are visible, making a turbine with a single black blade stand out insufficiently.

Nevertheless, painted blades may still offer a solution in the future. Instead of focusing on motion blur, as this study did, increasing contrast might be more promising. Follow-up research will need to determine whether this is indeed the case and how turbines can be made more visible to birds—for example, through the use of specific patterns and colors.