Offshore wind turbines could be killing 12 times more gannets than previously thought, experts have warned.
A study found the birds are most at risk of being hit when hunting for food.
Turbine blades must be a minimum of 22 metres (72ft) above sea level, and it was previously thought gannets flew well below this.
But using GPS trackers, researchers at the universities of Leeds, Exeter and Glasgow found that while hunting the birds flew at an average height of 27 metres – putting them within the blades’ reach.
Writing in the Journal of Applied Ecology they estimated up to 12 times more gannets could be killed by turbines than current figures suggest, and called for the minimum height to be raised to 30 metres.
They also warned that plans for two wind farms near the Bass Rock breeding colony in the Firth of Forth in Scotland could see 1,500 birds killed a year.
Dr Ian Cleasby, of the University of Exeter, said: ‘Our predictions – if realised in the field – are high enough to cause concern over the potential long-term effects on population size.’
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.
‘Increasing the distance between the tips of the spinning turbine blades and the sea would give gannets more headroom – so we strongly urge that the current minimum permitted clearance turbine height be raised from 22 metres to 30 metres.’
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.
‘It’s important we understand as much as we can about flight behaviour, and this study gives us further valuable insights on how they act in the marine environment.’
Hannah Smith of Scottish Renewables 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.’