New analysis of the height at which the seabirds fly has revealed that 12 times as many gannets could be killed by turbine blades than previous estimates, at planned wind farm sites which overlap with their feeding grounds.
The UK is home to two-thirds of the world’s northern gannets, which nest between April and September in spots such as the 70,000-strong colony on Bass Rock in the Firth of Forth the focus of the study published in the Journal of Applied Ecology.
Around 1,500 gannets nesting at Bass Rock could be killed each year by collisions with turbines at two planned offshore wind farms less than 30 miles away, approaching levels which could threaten the long-term viability of the population, it found.
Researchers from Leeds, Exeter and Glasgow universities said gannets had previously been thought to fly well below the 22-metre minimum height above sea level permitted for the sweep of turbine blade.
Previous analysis had been done by trained surveyors on boats estimating heights by eye, or by radar, both of which had limitations.
But the new assessment used miniature light-weight devices that logged GPS and barometric pressure, which were temporarily attached to the birds’ tails to allow researchers to track their flights in three dimensions while they flew out searching for fish.
While the gannets typically flew at around 12 metres when commuting between their nesting site and feeding grounds, the typical flight height when actively searching and diving for prey was 27 metres, potentially taking them into collision with the blades, the study showed.
The research also found the seabirds’ feeding grounds overlapped extensively with planned wind farm sites in the Firth of Forth, raising the risk of collisions.
A predictive model estimating how many of the birds would be likely to avoid the turbine blades showed about 1,500 breeding birds could be killed each year at the two nearest planned wind farms to Bass Rock – though there was uncertainty over what the actual numbers would be.
The paper called for raising the minimum permitted clearance height above sea level to 30 metres.
Co-author Dr Ewan Wakefield, of the University of Glasgow, said: “For the first time we’ve been able to track birds accurately in three dimensions as they fly from their nests through potential wind farm sites.
“Unfortunately, it seems that many gannets could fly at just the wrong heights in just the wrong places.”
WWF Scotland director Lang Banks said: “Offshore wind has an important role to play in safeguarding our rich marine environment over the long-term by reducing the impacts of climate change. Research like this can help contribute to ensuring those offshore wind farms are sensitively sited.
“Home to a quarter of Europe’s offshore wind resource, it makes sense for Scotland to tap into this clean energy source.
“With careful planning it should be entirely possible to harness this resource to help cut our climate emissions while still safeguarding the marine environment.”
Policy Officer for Scottish Renewables Hannah Smith said:
“It’s important to put this research into context. It focuses on developing a new method using a tiny sample of less than one percent of the total gannet population that can be found at the Bass Rock.
“Offshore wind farm developers in Scotland spend up to three years collecting detailed data on bird populations which is then scrutinised by various nature conservation bodies as part of their planning application. These assessments are then put before the appropriate Scottish Government specialists to ensure the work is scientifically robust as well as meeting all required national and international environmental legislation. This is a rigorous process designed to ensure that developments do not have an adverse impact upon our environment.”
Ms Smith added: “I am sure that the Scottish Government will look at this latest piece of research, along with all the other work by academic researchers, renewable energy developers and environmental agencies and assess if it is relevant to how they consider any future applications for offshore wind projects.”