Flying into turbulence

Wind farms are not the bird killer of popular imagination, but as more and more towers rise over the Australian landscape and as the country’s first offshore wind farm inches towards an end date, avian death counts are an easy headline.

Experts such as Emma Bennett, whose company Elmoby Ecology specialises in the effects of wind farms on birds and bats, say although turbines themselves don’t kill many birds when compared with habitat loss, climate change, bushfires, powerlines and other environmental threats, they’re a potential problem for vulnerable species such as the swift parrot and the white-bellied sea-eagle.

In 2019 Bennett produced one of the rare public estimates of wind-turbine bird strikes in Australia, saying each turbine could kill up to 17 birds a year.

In Victoria alone, which as of July had 1,079 operational wind turbines, that works out to up to 18,343 bird strikes a year at Bennett’s maximum – a number that still doesn’t come close to the 377 million birds estimated to be killed each year across all of Australia by feral and pet cats, however. She says the cost of monitoring is $20,000–$120,000 per turbine and it’s money better spent elsewhere.

You’re not just dealing with the literal lay of the land but the three dimensional space of air and how it moves.

But every wind farm site is its own unique entity, says BirdLife Tasmania spokesman Eric Woehler, because you’re not just dealing with the literal lay of the land but the three dimensional space of air and how it moves.

“The issues around wind farms are very complex, and the problem both from the regulatory and environmental perspective is the layout of every wind farm, in terms of topography, windflow and the arrangement of the turbines,” he says.

“Therefore the species at risk [at each site] is unique, so all we can do from one wind turbine proposal to the next is make generalisations and draw on broad principles.”

Some of the biggest names in this field, such as Ian Smales of ecology consultancy Biosis, are commercially involved in researching the impact of wind farms like the proposed 2.3 gigawatt (GW) Star of the South on avian populations.

If approved, Star of the South will be Australia’s first offshore wind farm. Its proposed location is tucked in behind the eastern shoulder of Wilsons Promontory in Victoria, which itself is an important staging site – a bird launchpad – for migrating short-tailed shearwaters (muttonbirds) and eastern curlews heading to Tasmania and beyond.

This means that Australia’s nascent wind energy industry, both built and planned, must look to innovations developed in the more mature wind industries of Europe and the US to help mitigate against bird deaths. Those technologies – which range from radar-equipped turbines that shut down when a specified bird approaches, to simply painting a blade black – combine high- or low-tech with our growing knowledge about the way birds travel through the air.

How do birds navigate and which species are most at risk?

Birds collide with wind turbines for many reasons.

Some, like birds of prey, are likely to be looking down for their next meal and not where they’re going. Others miss the slim sky-coloured blades travelling at surprising speed. Few expect an object to fall on them from above. Some are simply bad at flying.

Although it differs from species to species, birds generally have monocular sight on either side of their head which is attuned to seeing movement, and a narrow binocular sight in front. The former allows them to avoid obstacles at high speeds, but if they do not expect to see something in front of them that is less useful, says prominent Norwegian researcher Roel May.

May’s research into black turbine blades at the Smøla wind farm, about 500km north of Oslo, showed the species that collide most are the white-tailed eagle and grouse-like ptarmigan.

“While eagles are good flyers, they do not seem to care [about the turbines] or are more interested in con-specifics [members of the same species],” May says. “Ptarmigans are notoriously bad flyers, and we suspect them to fly into the actual turbine tower.

“So it is not that easy to say why birds avoid turbines. It is likely a complex combination of physiology (can they actually see what is in front of them given their eyesight?), behaviour (are they distracted due to foraging, con-specifics) and ecology (how good habitat encompasses the wind farm). This is also coupled with random bad luck.”

May says nearly half of the eagles that had collisions at Smøla were juveniles.

Studies around the world, from the US to Germany to Tasmania, indicate that it is raptors – birds of prey – that are among the most affected by wind farms, as well as large seabirds.

Wind turbine blades can travel at speeds of up to 290km/hour.

“Birds of prey, such as eagles, buzzards and vultures, use the same wind resources that turbines need to operate,” wrote University of Cape Town biologist Dr Megan Murgatroyd this year. “These large soaring birds use the wind to help power their own flight, using updraughts and thermals to gain height. This can make them particularly vulnerable to collisions with wind turbine blades, which can travel at speeds of up to 290km/hour and either eagles don’t see them or don’t perceive them as a threat until it is too late.”

Research suggests that in South Africa more than a third of birds killed by wind turbines are birds of prey, species that do not produce many young. So even a small number of deaths can have an over-large impact on population size.

In Australia, that scenario has played out in Tasmania. The 168 megawatt (MW) Musselroe wind farm in the state’s north-east, which has 56 turbines, caused at least 11 Tasmanian wedge-tailed eagle deaths and one white-bellied sea eagle death in six years due to collisions with turbines.

High tech low tech

High-tech collision reduction technologies are being developed and two are being rolled out with success in Tasmania, but it was a low-tech option that caught the bird world’s eye last year.

In a study that took place over 10 years, May’s Norwegian Institute for Nature Research (NINA) team showed that painting a single turbine blade black at the Smøla wind farm reduced bird fatalities by almost 72% on average. It was particularly effective for birds of prey, although the authors cautioned the experiment needed to be repeated at other sites to find out if it could be extrapolated to other areas and birdlife.

“To reduce collision susceptibility, provision of ‘passive’ visual cues may enhance the visibility of the rotor blades, enabling birds to take evasive action in due time,” the team wrote in their published research.

The more expensive and high-tech solutions include a model designed by Murgatroyd’s team that used eight years of tracking data of 15 Verreaux’s eagles in South Africa. The model predicts what airspace the birds use and therefore, optimal turbine sites. They say they can increase the amount of land area available to wind farms with this approach, but note the research is constrained by the type of bird and the small scale of the location covered.

Success in Australia is coming in the form of technology that shuts down turbines as specified birds approach.

The Musselroe wind farm began using radar technology developed by Dutch company Robin Radars in 2019, which Woehler says has been extremely effective.

The IdentiFlight aerial monitoring system, uses tower-mounted optical units and algorithms to identify flying objects as eagles, and then shut down turbines.

In central Tasmania last year, the 144MW Cattle Hill wind farm started an 18-month trial of the IdentiFlight aerial monitoring system, adapted from the US, to reduce wedge-tailed eagle deaths. It uses tower-mounted optical units combined with algorithms to identify flying objects as eagles, and then shut down turbines if the bird’s speed and trajectory indicate it’s on a collision path.

As of August 2021, Cattle Hill owner Goldwind was seeing some 400 shutdown messages a day across its 48 turbines. Each shutdown was for slightly more than two minutes.

The limitation of these technologies is that they’re tailored to specific bird species, and at this stage can’t recognise multiple species that might also be at risk of collision in the area.

No apex killer

While Australia is catching up, the majority of research on bird collisions and wind turbines comes from the northern hemisphere.

American researcher Dr Benjamin Sovacool suggested wind farms in the US and Europe killed some 7000 birds in 2006, yet the down- and upstream effects of habitat loss, pollution, and climate change meant nuclear plants killed an estimated 327,000 birds in the same year, and fossil fuel power stations some 14.5 million.

In the US and Canada, cats, buildings, moving vehicles, power lines, and agricultural pesticides are significantly more dangerous to birdlife than wind turbines, while in Norway the way wind farms alter and disturb habitats and create barriers are more responsible for bird deaths than turbine collisions.

But at the same time, a badly sited wind farm can also wreak havoc: the 1960s-era Altamont Pass wind farm in California, situated on a key avian migration route, was estimated to be killing 1300 birds of prey a year before changes were made from 2010.

Australia is at the beginning of its wind farm journey and as such, has a long way to go to ensure that birds, and other animals, can co-exist with the new world of renewable energy.