Eyes on the ground shield birds from death on wind farms

Clarissa Mars might have the most unusual job yet created by the renewable energy industry — keeping a lookout for approaching birds so the spinning turbines on her wind farm can be stopped before a fatal collision. 

Mars, 28, leads a team of 10 full-time observers at Excelsior wind farm near Swellendam, whose job it is to protect birds in a pioneering programme known as shutdown on demand (SDOD). 

The programme seeks to address one of the greatest concerns of environmentalists — that, while wind energy is preferable to fossil fuels, the turbines take a devastating toll on birds and bats. 

Top of mind for Mars is the endangered black harrier, the scarcest endemic raptor in Southern Africa, with only about 1,300 birds remaining. There is a crucial breeding colony in a remnant of natural renosterveld about 5km from the 13 turbines in the wind farm complex. 

“I love the black harriers, but they give me stress,” Mars said when the Sunday Times visited Excelsior, owned by Engie. She and her team, based at three vantage points, constantly scan the skies for black harriers and five other protected species — martial eagles, Verreaux’s eagles, Cape vultures, blue cranes and white storks.

When they spot one, they assess its flight pattern, and if it appears to be heading towards a particular turbine, they radio the control centre to stop the blades. It takes just over 40 seconds for the shutdown to happen. 

Mars says it is relatively easy to know what a Cape vulture is going to do — there is a large colony 30km away at Potberg in De Hoop nature reserve — but the small, fast black harrier is much more challenging. “With the black harrier, the flight patterns always change, especially when it comes to breeding season.” 

After it has caught prey on the ground, a black harrier will immediately soar vertically, as quickly and as high as it can. “So they don’t care about their surroundings. They can get hit by the blades.” 

Excelsior began operating four years ago, and since then the bodies of two black harriers killed by the turbines have been found. 

The species cannot afford such losses — a study cited by University of Cape Town ornithologist Rob Simmons says an additional five deaths a year could mean the bird goes extinct within 75 years. 

Simmons says the toll at Excelsior is likely to be higher than two — many fatalities at wind farms go unrecorded because scavengers such as mongooses quickly remove the carcasses. 

Mars’s stress about black harriers redoubled in May, when a pair of them began persistently foraging around the turbines. “We had a big shock ... There were 115 shutdowns just for the black harrier in one month,” she said. “We think they might start nesting 2km away.”

Odette Curtis-Scott, CEO of the Overberg Renosterveld Conservation Trust, praises Mars and Libby Hirshon, head of sustainability at Engie, for their efforts, but urges Engie to try an additional preventive measure — blade painting, which creates a flicker effect when the blades spin. 

“[This] could reduce collisions with turbines, with birds able to pick out the movement of the blades better when one is painted with a high-contrast colour. This could be an excellent opportunity to test this mitigation method,” said Curtis-Scott, whose NGO operates in the Excelsior area. 

Blade painting, or patterning, addresses the problem of “motion smear”, said John Gibbs, project leader for birds and renewable energy at BirdLife South Africa. “When birds look at wind turbines, what they see, we think, is a blur.” 

In a strong wind, the tip of a 60m wind turbine blade moves at about 280km/h. Mounted on a 90m tower, that creates a 120m-diameter circle of death at the same height that many birds fly.

[The raptors] like air, and where you’ve got wind uplift on the edge of an escarpment, this can be a big attraction for those birds, but it’s also where we end up putting wind farms

—  John Gibbs, BirdLife Africa

Blade patterning is being tested at Umoya wind farm at Hopefield on the West Coast. Hirshon said Engie was exploring the possibility of introducing it too. 

Gibbs said raptors in particular focused on the ground as they flew, looking for prey or carcasses. “Vultures are an example, they can see a small object on the ground when they’re looking for food. But they don’t look where they’re going.” 

He said automated SDOD using cameras, radar and AI should be tested. “It hasn’t been used to date in South Africa, though there are plans to install it in at least one location over the next 12 months.” 

He said the number of birds killed by turbines in South Africa varied by location, but for some it was as high as 50 a year, with an industry average of between two and three birds a year per turbine. 

“By definition, you want to put the turbines where the wind is best, and particularly with the raptors — the vultures, the eagles, the harriers — the thing they’re really good at is soaring on the thermals. They like air, and where you’ve got wind uplift on the edge of an escarpment, this can be a big attraction for those birds, but it’s also where we end up putting wind farms.” 

BirdLife is collaborating with the South African Wind Energy Association (Sawea) in trying to prevent casualties. “We are in the process of entering a memorandum of agreement to achieve our shared goals of bird conservation and protection,” Sawea said. “This agreement will outline areas of co-operation that promote the nature-friendly deployment and operation of wind-energy infrastructure.”

Engie, which has another SDOD programme in the Eastern Cape, recruits its observers from nearby communities, creating employment and generating interest in conservation. 

Mars, from Riviersonderend, studied conservation at college, but none of the nine other members of her team had any interest in birdwatching when they started out. “It’s people from the local communities, and they don’t know anything about any birds,”  Mars said.

An initial training period fixes that, and they continue to be tested on bird identification once a month. 

Hirshon said an unexpected benefit of the programme was how much new information about bird behaviour Mars and her team had discovered. 

“When we first started, we had no idea that we’d get certain species that were predictable and certain species that weren’t. It’s something that’s been very valuable for the bird specialist community — all these lessons we’ve learnt.” 

The programme was initially designed specifically to avoid vulture casualties. No vultures or eagles have been killed at Excelsior, said Hirshon.