Why wind farms paint one turbine blade black to protect birds

A simple paint job with a striking result

Wind farms sometimes paint a single turbine blade black, and the reason is bird safety. According to TechRadar, a long-running trial at the Smøla wind farm in Norway found that this small change cut the number of bird carcasses found nearby by about 70 percent.

The experiment began in August 2013, when researchers from the Norwegian Institute for Nature Research gave one black blade to each of four turbines and compared them with four neighbouring turbines left untouched. The team counted dead birds within 100 metres of the turbines across a study period spanning more than a decade, drawing on 7.5 years of counts before the painting and 3.5 years afterwards. The results appeared in the journal Ecology and Evolution in 2020.

The effect was especially clear for the region's white-tailed sea eagles, a somewhat rare species locally. The researchers cautioned that results might differ elsewhere, since bird populations vary, but the study offered real-world support for laboratory findings from 2003.

Why one dark blade makes a difference

The trick works because of how birds see moving objects. Animators use the term motion smearing to describe how fast-moving images blur into one continuous shape in the brain. To a bird, three plain rotating blades can look like a single translucent disc, making the hazard hard to spot.

Painting one blade black breaks up that pattern. The contrast gives birds a visual cue they can register, so they notice the spinning rotor and avoid it.

There are practical limits, though. Audubon has noted that the approach may not suit every species, particularly birds without the visual sharpness to see the contrast. Painting an operating turbine is also demanding work, requiring lifts and specialist crews trained to work at height.

Mixed results beyond Norway

The Norwegian success has not been repeated everywhere. Similar experiments in the Netherlands produced no measurable benefit, and the outcome appears to depend heavily on which bird species live in the area and how large their populations are.

That uncertainty has pushed newer projects to try different approaches. Dutch consortium Ecowende is fitting seven Vestas V236-15.0 MW offshore turbines with one red blade each, measuring 115.5 metres. Red was selected after weighing visibility at a distance against factors such as durability and heat management.

Do offshore farms need the fix at all?

Seabirds may face less risk from turbines than once assumed. A study by Vattenfall and Spoor at the Aberdeen offshore wind farm tracked 2,007 flight paths over 19 months and found no confirmed collisions. Birds typically kept 100 to 200 metres away from the turbines.

Taken together, the research suggests there is no single answer. Black blades clearly helped at Smøla, red blades are now being tested at sea, and some sites may not need painted blades at all. For wind farm operators, the lesson is that bird safety measures must match the local environment rather than rely on one universal solution.