The transboundary migratory routes of seabirds – taking them over open oceans and between national sea areas – makes weighing up their populations and the various threats posed to them by human activities a distinct test for management and conservation. One such challenge comes about then seabirds cross paths with wind turbines situated offshore.
Understanding the interplay between these dynamic birds and static energy structures and how the latter affect the former is being explored this week by the Joint ICES/OSPAR/HELCOM Working Group on Seabirds (JWGBIRD). The group is focusing its attentions on assessing the collision mortality of those birds which fly into the turbines and to what extent they are displaced by wind farm development.
The topic was outlined and the groundwork laid in a presentation by Bob Furness, seabird expert at UK environmental consultancy MacArthur Green, and Sue O’Brien, senior marine ornithologist at the UK Joint Nature Conservation Committee.
“This area of work is recognizing the concern about seabirds being impacted by offshore windfarms and the very rapid development of the offshore windfarm industry,” Furness explained. “A lot of these birds migrate and pass through many different parts of Europe and so they might be meeting windfarms during migrations. A question is how you assess the impacts on that sort of spatial scale.”
To put this scale into perspective, Furness offered the example of the red-throated diver, a species sensitive to structures like turbines as well as boats, which they therefore tend to avoid.
“A lot of the red-throated divers that winter in the southern North Sea come from breeding areas in Russia; they then seem to go to the German coast in the spring to fatten up before they go back to the breeding areas. They might come across windfarms off the English coast, and in the German and Dutch North Sea, and they might meet more of them when they migrate through the Baltic.”
Numbers of birds killed through collision or displaced from their habitats are the two most crucial impact parameters being looked at by JWGBIRD, said Furness
“There are issues in assessing collision mortality and displacement numbers. With collision mortality, it depends on the height at which the birds fly, which seems to vary depending on conditions. Gannets fly high over the water when they’re searching for food but very low over it when they’re commuting from A to B.”
“The species more likely to collide fly high over the sea – gannets, large gulls and kittiwakes. A lot of others like auks, sea ducks and divers fly very low, so there are unlikely to be collision concerns. This is because the blades are up high. One mitigation measure is to potentially raise the height of the blades to where fewer birds are flying.”
“Those likely to be affected by displacement are those which show strong avoidance to the turbines. Red-throated divers are particularly prone as are to some extent guillemots, razorbills, puffins and some sea ducks. It’s a different suite of species to the ones most likely to collide.”
Wind farms could also harm seabird populations through the ‘barrier effect’, where birds confronted with a row of turbines between feeding and breeding areas expend valuable time and energy circumventing them. Furthermore, there could be a loss of foraging habitat as many windfarms are built on shallow-water sandbanks, where some duck species feed on bivalves.
There are potential positive consequences though. Cormorants – which have wettable plumage – are able to stand on turbine platforms to dry off their feathers rather than come back to shore, meaning they can also hunt prey further out at sea. Fish are also colonizing waters around turbine bases, where rocks have been laid to help with scour protection. This could lead to increased fish stocks and more food for seabirds.
The wide-ranging nature of seabirds calls for an integrated, international approach – one reason why this year’s JWGBIRD meeting has a stronger representation from the Baltic countries.
“We’re starting to put all the information together,” continued Furness. “But it really needs to be done at an international level, that’s why ICES is a really good forum to discuss the issues and agree the best way forward. We’re trying to address how to bring together all the countries to coordinate the approach to assessment and consider the key gaps in our understanding. ”
“Almost all the focus of windfarm concern has been on the North Sea up to now, but it’s clear there are likely to be developments in the Baltic in the future. There are different species in the Baltic, but the same general issues. ”
The meeting saw Regional Seas Convention HELCOM and with it new co-chair Volker Dierschke were welcomed into the fold, joining other chairs Ian Mitchell (OSPAR) and Morten Frederiksen (ICES).
Studying wind farm impacts on seabirds was one of the group’s many Terms of Reference. Other topics included key work on OSPAR and HELCOM MSFD indicators, assessing the effects on seabirds of the new Common Fisheries Policy Landings Obligations, impacts of non-native mammal predators at seabird colonies, and complex interactions with fisheries.
Photo: Graeme Maclean, Flickr