Offshore wind farms 'threaten gannets'
Offshore wind farms could pose a more serious threat to Scotland's globally important gannet population than previously thought, scientists claim.
It is thought 12 times as many gannets could be killed by the turbines than previous estimates.
It follows research which showed the seabirds fly at greater heights when searching for food than other studies have suggested.
That is said to increase the risk of being hit by spinning turbine blades.
The calculation was made by scientists from the universities of Leeds, Exeter, and Glasgow.
Sources in the offshore wind industry have told BBC Scotland they believe the research must be treated with caution because it involved only a "tiny percentage" of the gannet population on the Bass Rock.
But conservationists have responded by pointing out the size of the colony means the scientists would have had to study 800 individual birds if they were to achieve a sample size of only 0.5 per cent of the population.
The Scottish government approved plans for four new offshore wind farms on the east coast in October 2014.
RSPB Scotland is already challenging the Scottish government's support for the developments in the courts, after arguing they "would be amongst the most deadly for birds anywhere in the world".
The Neart na Gaoithe offshore windfarm will have up to 75 turbines. It is due to be built 15km east of the coastline at Fife Ness.
The Seagreen Alpha and Seagreen Bravo developments will have a combined total of up to 150 turbines. They are to be installed 27 to 38km east of the Angus coastline.
The Inch Cape windfarm will have up to 110 turbines. It is located 15 to 22km east of the coast of Angus.
Source: Scottish government
The Bass Rock in the Firth of Forth is home to what has become the world's biggest gannet colony. An estimated 70,000 pairs of gannets now breed there, between April and September, each year.
The birds can cover distances of hundreds of kilometres when searching for food. The scientists point out the Bass Rock is less than 50km from proposed turbine sites.
The blades of offshore wind turbines must be at least 22m above sea level, due to the need to protect shipping. It had been thought gannets flew well below that height.
But research carried out in the Firth of Forth shows the birds fly at an average height of 27m above sea level when searching and diving for prey. The scientists used lightweight GPS logging devices and barometric pressure loggers, temporarily taped to the gannets' tails, to track the birds as they flew from the Bass Rock to search for fish.
Until now, data had been gathered by trained surveyors on boats, who estimated the height at which the birds flew, or by radar.
Prof Keith Hamer of the School of Biology at Leeds University oversaw the new research.
He said: "Our study highlights the shortfalls in current methods widely used to assess potential collision risks from offshore windfarms, and we recommend much greater use of loggers carried by birds to complement existing data from radar studies or observers at sea."
The data gathered in the latest study was used to predict that around 1,500 breeding birds could be killed each year at the two planned wind farms nearest to the Bass Rock.
Dr Ian Cleasby, of Exeter University and the lead author of the study, cautioned: "There's a lot of uncertainty over how many birds would actually be killed this way. But 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: "It seems that many gannets 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.
"We strongly urge that the current minimum permitted clearance turbine height be raised from 22m to 30m above sea level."
The renewable energy industry insists the potential environmental impact of offshore windfarms is already carefully examined before consent is granted by ministers.
Hannah Smith, of Scottish Renewables, said: "It is important to put this research into context. It focuses on developing a new method using a tiny sample of less than 1% of the total gannet population that can be found at the Bass Rock.
"Offshore windfarm 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."
In a statement, the Scottish government told BBC Scotland: "This study, although limited in scope, makes a useful contribution to improving our understanding of seabird behaviour.
"Harnessing our natural resources through offshore wind helps to decarbonise our electricity supplies as a key plank of tackling climate change, which we know is itself having a significant effect on bird populations."
A spokesman for RSPB Scotland said: "This is an enormously useful and scientifically sound contribution that highlights how little we know about what seabirds do when they are out at sea and away from their nesting sites around our coast.
"RSPB Scotland is currently involved in a Judicial Review of the four offshore windfarm projects in the Firths of Forth and Tay. Given the ongoing legal proceedings, it would not be appropriate for us to comment further on the implications of this research in relation to these cases."
The study was funded by the Natural Environment Research Council and the Department of Energy and Climate Change. It has been published in the Journal of Applied Ecology.