How high do seabirds fly? We don’t know, but offshore wind developers need to find out

Bigger turbines that stand higher above the ocean could reduce the number of seabirds being hit by blades in the future offshore wind farms in the southern oceans, researchers think.

A new paper in the Journal of Applied Ecology offers offshore wind developers in the country’s south details on how high, how fast and at what time of day albatrosses, petrels, shearwaters and storm-petrels fly. 

The review study looked at 119 ocean-going birds, and found that a third of these big seabirds are flying at night and a third spend time flying during the day and the night.

Then, to predict how many collisions might happen, the researchers used flight height to estimate the amount of time spent in a turbine’s rotor swept zone (RSZ), flight speed to estimate the probability of being struck by rotating blades, and time sent flying at night to suggest how many collisions might happen during the unsurveyed night-time.

“This will help scientists and policy makers better understand and mitigate the risks of these unique seabirds colliding with offshore wind turbines,” said Monash University’s Mark Miller, lead author on the paper.

“Australia is developing a comprehensive environmental and cultural impact assessment process for new wind infrastructure, but with no offshore wind farms in the Southern Hemisphere yet, there are still key gaps in knowledge.

“One of these is that we currently have a poor understanding of seabird flight behaviour and how this might influence collision risks for iconic species such as albatrosses and petrels.”

But while the data points on flight speed and time of day can go straight into collision risk models being designed by offshore developers, scanty data on flight height is a problem, Miller told Renew Economy. 

“We were hoping to find lots of information on flight height but we found nothing,” he says.

“Just 13 or 14 species had a single or two data points on how high they fly.”

It means offshore wind developers need to fill the gap with their own studies, but the federal government is also working on that too. 

Seven projects focusing on offshore bird collisions or ecology are currently being sponsored under the Renewables Environmental Research Initiative to create a baseline that commercial projects can be measured against. 

Data points from the research paper showing when and where big offshore seabirds appear in the southern hemisphere oceans.

The study also highlighted the need for developers to fully understand the ecology of the birds in the areas they intend to operate in order to draw up collision risk management strategies. 

“Our study has shown that storm-petrels regularly fly at night, and there is evidence that they display light attraction,” the researchers wrote in the paper. 

“As offshore wind turbines require lighting for navigation purposes, storm-petrels may be attracted towards them at night and become disorientated (possibly circling the light source for hours, thereby increasing their risk of collision.”

It’s a strategy that Australia’s leading offshore wind developer is already using. 

In November last year, plans for the 2.2 gigawatt (GW) Star of the South wind farm in the Gippsland zone cut the number of turbines and lifted the blades higher off the ocean.

The plans now foresee 150 bigger, more powerful turbines instead of 200, and changed the design to lift the gap between the ocean and turbine blades from 25 metres to 35 metres. 

The company said the decision was based on looking at “bird flight height data”, and to provide “a safe zone for seabirds to fly and forage.”

Balancing one harm against another

Bird strikes are an emotionally charged topic onshore already.

In June, Victoria issued a handbook to guide developers on how to “avoid, minimise, mitigate and compensate for impacts on threatened bird and bat species,” as approvals for large-scale wind and solar projects ramp up.

It clarifies expectations for onshore wind developers for managing impacts on threatened bird and bat species, and describes the methods that can be used to manage these impacts.

While zebra striped blades have been proposed, by researchers, as a preventative for bird collisions with turbines, it’s unclear whether any offshore developers are planning on using this design in Australia. 

Balancing the good environmental outcomes of renewable energy developments – the end of fossil fuels in the electricity grid – with the impact that building and operating them have on their immediate surrounds, is a constant.

Collaborating over this kind of data is one way the offshore sector can ensure the transition benefits people and wildlife, says Monash University’s Rohan Clarke. 

“Our job is to help deliver the best possible outcomes for biodiversity, and addressing climate change through large-scale action is essential to that goal,” said Clarke, who was one of the authors of the paper. 

“One of the key challenges we face is what’s known as the ‘green-green dilemma’, where initiatives designed to reduce environmental impact, such as renewable energy development, can unintentionally harm other ecological values.

“But we must identify evidence-based solutions to these competing priorities, because climate change remains the single greatest threat to biodiversity.”

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