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Wind turbines may affect eagles

What do cold fronts and black eagles have in common? In the Grootwinterhoek mountains the eagles use the cold fronts as prime weather for hunting, capitalising on the low cloud and poor visibility that sweeps in.

Raptor expert Adri Barkhuysen, of East Cape Diverse Consultants, describes this in a report which he has just submitted as part of the initial assessment of the planned Inyanda-Roodeplaat Wind Farm.

Initiated by Johannesburg- based Inyanda Energy Projects, the planned farm is sited 30km north-west of Uitenhage, on the edge of the Groendal Wilderness Area, slap bang in the middle of the prime black eagle range of the Grootwinterhoek.

The black eagle’s hunting technique, combined with the introduction of turbines could be bad news for this important population, Barkhuysen warns.

His report follows coincidentally on the news just out of the US of a government study which has found that at least 67 eagles have been killed by wind turbines in the last five years and the number, as the study says, could be much higher.

According to the Inyanda-Roodeplaat Project report compiled by Coastal and Environmental Services (CES), there will be 35 turbines generating 149MW clustered in a footprint of 60ha within the total 12000ha wind farm. Dimensions are still being finalised, but the turbines would be similar to the giant at Coega. Rotor diameter would be up to 130m. Blade tip height would be up to 250m.

In his report submitted to Wild Skies Ecological Services, which was in turn subcontracted by CES, Barkhuysen refers to a study he conducted in 2002-2005. Aided by landowner surveys and Birdlife Eastern Cape and Mountain Club volunteers, he identified 27 nesting pairs of black eagles and a “reserve bank” of 14 non-territorial “floaters” in a 50km stretch along the arid northern slopes of the Grootwinterhoek and adjacent more open land.

The study showed that the nests, especially in the mountains, tucked away in pristine kloofs, had good breeding success. But, as Barkhuysen notes, this pattern can quickly change. If the female is killed then obviously breeding is directly affected, but if the male is killed then territorial dominance, a key breeding condition, is lost. If both are killed, the population can quickly slide.

He found that after a cold front there would be two to four dassie carcasses, distinctly more than at other times, piled on the nests. This phenomenon seemed to indicate that the black eagles’ hunting is more successful during cold fronts, he explains. “It is likely that the cloudy and windy conditions, hence low visibility, could assist them to pursue and capture their prey.”

Although these birds are extraordinary fliers, this hunting technique could prove fatal if a giant and lethal new presence is introduced, he says. “Searching for or seeing dassie prey between the rocks would be somewhat different from reacting to avoid an unexpected turning turbine blade in mid-air mist and gust.”

Because they are silent birds, another key feature of black eagles is their territorial displays. These pendulum dives above their nests might also make them vulnerable to colliding with turbine blades, he says. “When neighbouring pairs counter-display the territorial aggression might overcome the eagle’s learned behaviour of remembering or even noting the turbines. Even if one pair falls out of the system the ripple effect could be devastating because the displays by each are done for the benefit of their black eagle neighbours.”

According to the scoping report, key Inyanda associate Ronnie Watson is a key purchaser of the land for the wind farm. (Brother of Eastern Cape rugby supremo Cheeky, Ronnie featured in The Herald in July after being confronted by the forestry department for illegally clearing indigenous bush on his Theescombe property).

According to the report, as part of the project, the developer’s intention is to link the presently divided eastern and western sections of the Groendal wilderness, thus supporting conservation.

That sounds great. But how does it gel with the threat to the black eagle and the many other raptors and birds that inhabit Groendal?

Are there viable mitigation measures?

Is it acceptable to site a wind farm on the edge of a declared protected wilderness area, one of the few fast-dwindling places where, as Barkhuysen says, “eagles can just be eagles”? Will this project fit into the long-awaited strategic plan being drawn up by the CSIR which is seeking to ensure the best spots for wind farms in terms of optimum wind but also least environmental sensitivity?

Renewable energy inclusive of wind farms is the only way to go for our power needs. But we need to do it right, otherwise we are just going to be creating another environmental crisis.