Wind turbine lights attract bats, a 2025 study found
Wind turbine lights attract bats, a 2025 study of 3 wind farms in northeastern Germany found, because a red light meant only to warn aircraft can also draw wildlife toward the turbine. Researchers compared bat activity near turbines with the red light on all night, every night, against turbines fitted with an aircraft detection lighting system, a radar unit that switches the light on only when it detects a plane nearby. The radar controlled turbines were lit for an average of 12% of the night, against every night, all night, for the standard lights. All turbines shared the same hub height, 100 meters, so turbine size does not explain the difference.
In June 2021, the team recorded 28,966 bat passes at 22 site triplets, each one comparing a constantly lit turbine, a radar controlled turbine and a spot with no turbine within 2 kilometers. Bats navigate by bouncing sound off objects, called echolocation, and the medium range group, the one that travels farthest and includes the common pipistrelle, made up the largest share of activity recorded at wooded edges, 74.7%. The short range group, whose calls carry the least distance, made up the smallest share, 7.2%.
Medium and short range figures are stated directly in the study. The long range figure, 18.1%, is arithmetic performed for this article, the remainder after subtracting the other 2 shares from 100%, since the study states only the first 2 directly.
Show the numbers
| Medium range | 74.7 |
| Short range | 7.2 |
| Long range | 18.1 |
Only 4 studies anywhere had tested this before
The researchers tested 6 combinations of bat group and habitat type. In 4 of the 6, bat activity was significantly higher near the constantly lit turbines than near both the unlit control sites and the radar controlled turbines, with the radar controlled sites statistically similar to having no turbine there at all. Before this study, only 4 studies anywhere had tested whether turbine aviation lighting attracts bats, all of them in North America, and a 2014 guidelines document from the treaty body UNEP EUROBATS had already concluded the effect did not exist, citing a study that rejected it. Reading the 2025 study against that 2014 conclusion means this is the first solid evidence for a mechanism the field had spent a decade treating as settled and wrong.
An existing fix already cuts bat deaths, but costs power
Wind turbines already kill an estimated 200,000 bats a year in Germany, and more than 500,000 a year in the United States, according to Bat Conservation International. The current standard fix, called curtailment, pauses turbine blades at low wind speeds, when bats are most active, cutting deaths by more than 60% but cutting the power output of a turbine by more than 10% along with it. Cutting the light duration instead costs nothing in electricity, since the turbine keeps spinning as before. Germany already requires the radar controlled system on some turbines, and the study authors say that mandate may spread to other countries because it costs nothing to adopt.
Approximate. Source 2 states these as around 50,000 in Canada, more than 200,000 in Germany and more than 500,000 in the United States, not exact counts.
Show the numbers
| Canada | 50,000 |
| Germany | 200,000 |
| United States | 500,000 |
The study shows less attraction, not yet fewer deaths
The study measured bat activity at ground height in June, months before the autumn migration when most turbine bat deaths actually happen, so it shows a drop in attraction near the turbine, not yet a drop in bodies on the ground. Winifred Frick, chief scientist at Bat Conservation International, said the wider goal for the industry is compatibility, not a trade off.
We want to find ways in which we can maximize energy production, but do that in a way that is ecologically responsible and not causing biodiversity loss.
Winifred Frick, chief scientist at Bat Conservation International, quoted in source 2. Source 2.