One of the great drivers of the global energy transition are wind turbines. Of course, they have been carrying a silent problem for decades: they kill animals. Wind turbines kill 368,000 birds a year in the United States and Canada alone, according to this study published in PubMed. The data for Europe is more fragmented and varies greatly by country and type of facility: in Germany for example place mortality between 100,000 and 250,000 birds per year and SEO/BirdLife esteem that between 1.2 and 4.6 million birds die per year (data from 2023).
Given that the expansion of wind power seems unstoppable, the question is how to minimize these deaths, e.g. with self-adaptive speed blades. A research team from the University of Helsinki and the University of Exeter has just publish a proposal unexpectedly simple but effective (judging by its results): painting the blades with the colors of poisonous animals, appealing to one of the most solid principles of evolutionary biology.
Those dangerous snake-painted wind turbines. The research team exposed birds to videos of turbines spinning in four color schemes: standard white, a black blade, red-white stripes, and a red-black-yellow biomimetic pattern that was inspired by coral snakes and dart frogs. The result was clear: the birds systematically avoided the blades with the biomimetic pattern and moved closer to the white ones.
The remarkable thing about the discovery is why it works. It was not necessary for the birds to learn in the experiment to associate those colors with danger like Pavlov: They were already learned from home. The key is in aposematism, just the opposite of camouflage: signaling danger with colors, something that has been engraved in the nervous system of birds for millions of years. The team simply transferred that evolutionary signal to a huge steel structure.
Why is it important. The United States Renewable Energy Institute calculate that per megawatt installed the turbines kill between two and six birds and between four and seven bats, figures that seem small but are considerable on a global scale: the world’s wind capacity already exceeds 1,000 GW installed, according to the Global Wind Energy Council. Reducing the death of animals is the main reason, a good practice that is even more relevant if the species in question has a small population. If the solution is also something as cheap as changing the paint color, the cost-benefit in terms of conservation is difficult to ignore.
Context. Aposematism is a documented evolutionary mechanism for almost two centuries: The idea is that certain toxic or dangerous animals warn of their danger with bright colors. The winning combination to scare you is red-black-yellow, universally recognized as a sign of toxicity among vertebrates.
What this study does is apply this principle outside of the natural world by projecting it onto an industrial infrastructure. It is not a pioneer: there is a previous investigation in Norway in which they tried painting a blade black to break the optical illusion of a “still hole” created by the spinning turbines and the results were already promising. This new study goes a step further by actively exploiting the perception of danger.
How it works. The birds process color in a radically different way from humans. They have four types of photoreceptors instead of three, which gives them tetrachromatic vision and allows them to detect ultraviolet. In short: they appreciate contrast better than humans, so apostematic signals are extraordinarily striking to them. For the experiment they used touch screens designed specifically for birds, so that they interacted with them by moving closer or further away from the stimuli, thus allowing them to precisely quantify how they behaved in response to each pattern. The biomimetic pattern was the most avoided of all.
Yes, but. As the research team acknowledges in the paper, all tests were carried out in the laboratory, with birds in front of screens, not with wind turbines spinning in the open field. Perception distance, approach angle, flight speed or weather conditions are variables that the experiment does not replicate. Taking it to the real world can be a very different story.
Furthermore, the study was carried out with a limited number of species. Aposematic responses depend on the evolutionary history of each lineage and whether that group has coevolved with those dangerous species in its territory. Come on, what may be useful for birds native to an area may be useless for migratory raptors or for species affected in specific wind farms.
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Cover | Gonz DDL and David Clode Alfonso Castro
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