Painting one of a wind turbine's three blades black was associated with a reduction of almost 74% in annual bird deaths, according to a study at a wind farm in Spain. Researchers compared four turbines with a painted blade with another sixteen that kept all their blades white. The finding suggests that a simple intervention may help reduce an environmental problem associated with wind power, although its effectiveness needs testing on a larger scale.
The idea is based on how rotating blades become visible. As they move, large white blades can form an almost transparent blur that birds struggle to distinguish. A blade of a different colour could, in theory, interrupt this visual blur, making the turbine easier to see and helping birds avoid it.
The experiment took place at the El Ruedo wind farm in Cádiz, owned by Acciona Energía. Between 2020 and 2021, the company painted one blade black on each of the four turbines receiving the intervention, while the other sixteen formed the control group. From 2012 to 2024, before and after painting, daily searches for dead birds were carried out beneath all twenty turbines, and the findings were recorded.
Similar results have emerged in other countries, although not all studies agree. In Norway, painting one blade black was associated with a reduction of more than 70% in annual bird deaths, while in South Africa, using red paint on one of the three blades was associated with an 83% reduction. By contrast, a study in the Netherlands found no significant reduction, limiting how far the positive findings can be generalised.
Wind power is a useful tool for tackling the climate crisis, but its expansion may increase bird deaths, according to the study's lead author, Roel May, of the Norwegian Institute for Nature Research (NINA). In a message to Mongabay, the researcher referred particularly to migratory songbirds, as well as many long-lived birds of prey and other soaring birds. As he explained, the long lifespans and low reproductive rates of some species make their populations particularly vulnerable to additional mortality.
In the US, wind turbines are estimated to kill up to one million birds each year. Although substantial, this number is much smaller than the billions of birds killed by cats and the further one billion that die annually from collisions with buildings in the same country. This comparison places losses from wind power in the broader context of threats to birds.
Implementing the intervention also presents practical difficulties. In the Spanish study, the blades were painted after the turbines had already been installed and were operating, a difficult and expensive process. According to May, painting during manufacture is easier and cheaper, but manufacturers remain cautious, citing concerns that black paint may increase blade heating or alter their weight.
So far, trials aimed at reducing bird deaths by painting turbine blades have been conducted on a small scale, the researcher points out. He hopes the industry will expand its use of the method, systematically monitoring its results and drawing on practical experience. The positive findings offer a way to reduce collisions, while the different result in the Netherlands underlines the need for further evaluation.
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