Offshore wind farms which are to be built in waters around the UK could pose a greater threat to protected populations of gannets than previously thought, according to a new study by researchers at the universities of Leeds, Exeter and Glasgow.
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 Keith Hamer.
The research paper, "Three dimensional tracking of a wide-ranging marine predator: flight heights and vulnerability to offshore wind farms", by Cleasby et al, is available from the press office.
Professor Keith Hamer is available for interview. Contact Ben Jones in the University of Leeds press office on 0113 343 8059 or email B.P.Jones@leeds.ac.uk
*Source: RenewableUK: http://www.
University of Leeds
The University of Leeds is one of the largest higher education institutions in the UK, with more than 31,000 students from 147 different countries, and a member of the Russell Group research-intensive universities.
We are a top 10 university for research and impact power in the UK, according to the 2014 Research Excellence Framework, and positioned as one of the top 100 best universities in the world in the 2014 QS World University Rankings. http://www.
University of Exeter
The University of Exeter is a Russell Group university that combines world-class research with very high levels of student satisfaction. Exeter has over 19,000 students and is ranked 7th in The Times and The Sunday Times Good University Guide league table, 10th in The Complete University Guide and 9th in the Guardian University Guide 2015. In the 2014 Research Excellence Framework (REF), the University ranked 16th nationally, with 98% of its research rated as being of international quality. Exeter was The Sunday Times University of the Year 2012-13.
The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the last few years; including landmark new student services centres - the Forum in Exeter and The Exchange on the Penryn Campus in Cornwall, together with world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute. There are plans for further investment between now and 2016.
For further information: Louise Vennells, University of Exeter, Press Office, +44 (0)1392 722405 or 722062 firstname.lastname@example.org
University of Glasgow
The University of Glasgow has been inspiring people to change the world for over 550 years and is a member of the prestigious Russell Group of leading UK research universities. As a world top 100 university with annual research income of more than £181m and overall student satisfaction rate of 91%, the University of Glasgow is committed to delivering world class research at the same time as the highest standards of teaching and education.