It was previously thought that gannets, which breed in the UK between April and September each year, generally flew well below the minimum height of 22 metres above sea level swept by the blades of offshore wind turbines.
However, while this is the case when the birds are simply commuting between their nest sites and distant feeding grounds, this new study shows that they fly at an average height of 27 metres above sea level when actively searching and diving for prey. Crucially, the study also shows that the birds' feeding grounds overlap extensively with planned wind farm sites in the Firth of Forth, heightening their risk of colliding with turbine blades.
The researchers estimate that up to 12 times more gannets could be killed by turbines than current figures suggest, although they stress that the figure is based on calculations using current typical turbine sizes, which could be different to those actually installed, and that there is great uncertainty over actual turbine avoidance rates. Previously data on gannet flight heights were obtained by one of two methods: trained surveyors on boats estimating heights by eye, or radar, which usually has a limited range of about 6km and is costly. The researchers conclude that more sophisticated methods of assessing risk should be adopted urgently.
Professor Keith Hamer, of the School of Biology at Leeds, oversaw the study, published today in the Journal of Applied Ecology. His research group, together with colleagues from Exeter and Glasgow, based their work at Bass Rock, the world’s largest colony of gannets with some 70,000 breeding pairs, situated in the Firth of Forth in south-east Scotland, less than 50 kilometres from several planned wind farm sites. He said: “Our study highlights the shortfalls in current methods widely used to assess potential collision risks from offshore wind farms, and we recommend much greater use of loggers carried by birds to complement existing data from radar studies or observers at sea.”
Dr Ian Cleasby, of the University of Exeter and lead author of the study, said: “Previous data had seriously underestimated the number of birds potentially at risk of colliding with turbine blades. 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.
“Our predictions suggest extra care be taken when designing and assessing new wind farms to reduce their impact on gannets.”
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 22m to 30m above sea level.”
Using miniaturised light-weight GPS loggers and barometric pressure loggers, temporarily taped the birds’ tails, the researchers tracked the flights of gannets in three-dimensions as they flew out from the Bass Rock, searching for fish.
They then used the data in a predictive model which suggested that, based on available estimates of the proportion of birds that would be likely to avoid the turbine blades, about 1,500 breeding birds could be killed each year at the two planned wind farms nearest to the Bass Rock. The government expects offshore wind power could supply between eight and 10% of the UK’s annual electricity supply by 2020. It currently supplies about 4%, according to the latest official figures.*
The study was funded by the Natural Environment Research Council and the Department of Energy & Climate Change (DECC). A further, more extensive tagging study to improve understanding of gannet flight heights and behaviour has been funded by DECC in 2015. This work is being led by Professor Hamer.
Graham Askew, Simon Walker, BBSRC (Jan 2018), £699,781
Jennifer Tomlinson, Royal Society (Jan 2018), £512,801
Jennifer Tomlinson, Royal Society-Research Fellows Enhancement Award (Dec 2017), £94,681
Helen Miller, AB AGri Grant (Dec 2017), £73,600
Simon Walker, Royal Society Enhancement Award (Dec 2017), £10,000
Carrie Ferguson, Bryan Taylor, Harry Rossiter, The Physiological Society (Dec 2017), £7,392
Ralf Richter, Royal Society (Dec 2017), £6,000
Christine Foyer, British Council Newton Fund (Dec 2017), £49,840
Adrian Whitehouse and colleagues in School of Chemistry and University of Liverpool, MRC (Nov 2017), £622,319
Michelle Peckham, Neil Ransom, MRC (Nov 2017), £495,159
Dave Lewis, British Council India (Nov 2017), £22,540
Elton Zeqiraj, Royal Society (Nov 2017), £15,000
Hannah Dugdale, Royal Society (Nov 2017), £15,000
Shaunna Burke, Cancer Research UK Innovation Grant (Nov 2017), £20,000
Alex O'Neill and colleagues in Chemistry, BBSRC (Nov 2017), £431,865
Jessica Kwok, Wings for Life (Nov 2017), £87,365
Tom Bennett, BBSRC (Oct 2017), £523,679
Neil Ranson, Darren Tomlinson, BBSRC (Oct 2017), £494,318
Nikita Gamper, BBSRC (Oct 2017), £490,426
Amanda Bretman and colleagues from UEA, NERC (Oct 2017), £430,886
Juan Fontana, Rosetrees Trust consumables grant (Oct 2017), £22,500
Helen Miller, DSM Nutritional Products AG (Sep 2017), £69,988
Neil Ranson, Juan Fontana, Mark Harris, Michelle Peckham, Ralf Richter, Peter Stockley, Patricija Van Oosten-Hawle and colleagues in Engineering, FMH and MAPS, Wellcome Trust Equipment Call (Sep 2017), £418,000
Jamie Johnston, Physiological Society (Sep 2017), £10,000
Frank Sobott, Adrian Goldman, Mark Harris, Andrew Macdonald, Stephen Muench, Sheena Radford and colleagues in FMH and MAPS, Wellcome Trust Equipment Call (Aug 2017), £415,000
Ralf Richter, David Brockwell, Eric Hewitt, Jessica Kwok, Emanuele Paci and MAPS/FMH, BBSRC (Jun 2017), £600,000
Eric Blair, Adrian Whitehouse, Nicola Stonehouse, Alison Baker, Richard Bayliss, Joan Boyes, Ryan Seipke, Sally Boxall and MAPS/FMH, BBSRC (Jun 2017), £376,000
Stefan Kepinski, Yoselin Benitez-Alfonso, Tom Bennett, Michelle Peckham, BBSRC (Jun 2017), £331,000
Roman Tuma, Lars Jeuken, Paul Millner, Sheena Radford, Peter Stockley and MAPS/FMH, BBSRC (Jun 2017), £222,000
Vas Ponnambalam, Darren Tomlinson, Stephen Wheatcroft, BHF (May 2017), £107,878
Graham Askew in collaboration with Bangor University, BBSRC (Mar 2017), £477,383
Stephen Muench, BBSRC (Mar 2017), £132,945
Nic Stonehouse, MRC (Mar 2017), £906,341
Bill Kunin, Steve Sait, BBSRC (Mar 2017), £602,831
Adrian Goldman, EU (Mar 2017), £546,576
Sheena Radford, Wellcome Trust (Mar 2017), £1,836,482
Beatrice Filippi, Royal Society (Mar 2017), £15,000
Tom Bennett, Royal Society (Mar 2017), £15,000
Jamie Johnston, Royal Society (Mar 2017), £15,000
Ryan Seipke, BBSRC (Feb 2017), £52,116
Mary O'Connell, BBSRC (Feb 2017), £46,986
Hannah Dugdale, NERC (Feb 2017), £504,138
Anastasia Zhuravleva, EPSRC (Jan 2017), £100,792