Gannets are at risk from wind farms

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 the 70,000-strong colony on Bass Rock in the Firth of Forth, Scotland, 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 50km (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 (72ft) 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 (39ft) when commuting between their nesting site and feeding grounds, the typical flight height when actively searching and diving for prey was 27 metres (89ft), 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.

An RSPB Scotland spokesman said: “This is an enormously useful study; a really valuable contribution to our knowledge about the behaviour of seabirds when they are out at sea and away from their nesting sites around our coast.”