Sound waves could be used to prevent millions of birds flying into wind turbines

Devices that use focused sounds to prevent birds from crashing into tall structures, or gathering in places where they are not wanted, have been developed by scientists.

It is thought they could be employed to prevent the deaths of millions of birds every year that collide with wind turbines.

When other structures such as mobile phone masts and buildings are taken into consideration, the number of bird deaths resulting from collisions is thought to go into the billions.

At the same time, birds cause an enormous amount of damage to human infrastructure, feeding on agricultural products and flying into aeroplanes.

In response to these problems, behavioural biologist Dr John Swaddle has helped develop technological solutions that use sound waves to drive birds away from areas where they are causing disruption.

“The fundamental knowledge of how birds behave and respond to sound helps us derive these new technologies and solutions,” Dr Swaddle told attendees at the annual meeting of the American Association for the Advancement of Science.

Along with his collaborators, Sonic Nets and Acoustic Lighthouses, he has developed two projects to combat the problem.

Sonic Nets have already been extensively trialled, and are known to be effective devices to reduce bird numbers in specific locations such as fields full of ripening crops.

The speakers in these devices emit “pink noise” designed to disrupt the communication of gathering birds. Birds that cannot “talk” to each other are also unable to warn each other about approaching danger.

This tends to make birds nervous, meaning they will quickly disperse.

“The idea is that we’re broadcasting sounds that maximally interfere with the way birds communicate with each other,” Dr Swaddle said.

The Acoustic Lighthouse is a newer concept, and one that Dr Swaddle would like to see applied to prevent bird collisions with wind turbines in particular.

“There’s a lot of interest in developing near-shore or offshore wind energy. Putting large, rotating structures that look like mincemeat-makers in the sky isn’t going to be good for the birds,” Dr Swaddle added.

“We know that there’s a risk to bird populations. That risk is not evenly spread across the world. It’s concentrated in certain areas, because wind is concentrated in certain areas. That’s where the wind turbines are – and that’s where bird movement are sometimes concentrated, especially during migration.”

A directional speaker mounted on a wind turbine can be used to alert approaching birds to the approaching danger.

Bird anatomy means that when they are in flight, their focus is not directed ahead. Their eyes are located on the sides of their heads, and while they may turn their heads from side to side to look downwards, their forward-facing vision will not be in high resolution.

Scientists have suggested birds are not prepared for the presence of tall, man-made structures in their aerial environment.

“Birds in flight may predict that the environment ahead is not cluttered,” Professor Graham Martin, a specialist in bird senses at the University of Birmingham wrote in a paper published in the journal Ibis.

“Even if they are facing forward, they may fail to see an obstacle as they may not predict obstructions; perceptually they have no ‘prior’ for human artefacts such as buildings, power wires or wind turbines.”

However, if birds are shocked into looking ahead by bursts of sound, they will suddenly stop in the air, averting collision. This was demonstrated in a paper co-authored by Dr Swaddle in the journal Integrative and Comparative Biology.

“All that’s missing is the brake-screeching sound,” he said.

These issues are particularly pertinent in Virginia, where Dr Swaddle is based at Virginia's College of William and Mary. Not only does the state sit underneath a major bird migration route, it is also being eyed up as a prime setting for wind turbines.

While the Acoustic Lighthouses are still under development, Sonic Nets are already being commercialised in a partnership with local business Midstream Technology.