New research just published in the journal Resonance and migrationHe used the latest tracking technology to investigate how one of Britain’s largest ducks, Shelduck, interacted with offshore wind turbines as they migrated across the North Sea.
Their findings reveal – for the first time – the length, speed and altitude of this journey.
Offshore wind farms are a major part of many governments’ strategies to reduce carbon emissions and mitigate the effects of climate change. However, it is important to understand how it might affect wildlife.
The risk of colliding with wind turbines is a particular concern for migratory species that travel by sea, and there is also a potential increase in the cost of energy if wind farms serve as a barrier that migratory birds have to fly around.
The majority of the British and Irish Sheldacks are subject to “fall migration” to the Wadden Sea, which stretches along the coasts of the Netherlands, Germany and Denmark. They make this trip every year in late summer, after they have finished breeding.
Once there, they replace their old, worn out feathers and are flightless in the relative safety of the Wadden Sea, before returning to Britain when molting is complete. However, on the journey to and from the Wadden Sea, Shelduck must cross the North Sea and navigate an increasing number of wind farms en route.
Scientists from the British Ornithological Fund (BTO) used the latest technical markers to trace four Sheldacks from the special conservation area of the Alde-Ore estuary on the Suffolk coast to the Wadden Sea. Each bird took a separate route through the North Sea, and used previously unreported stopping sites in the Dutch Wadden Sea, before continuing to clear the sites at Helgoland Bight off the coast of Germany. Incredibly, one bird traveled back and forth between the Dutch and German Wadden Seas four times, adding an additional 1,000 kilometers to its migratory flight.
The reasons for staying a mystery.
“Having a working knowledge of species migration movements is an essential first step in understanding the risks that offshore wind farms may pose to Shelduck populations and other species,” said Ros Green, a research ecologist at BTO and lead author of the paper. Shelduck’s flight speeds and altitude, providing additional vital information on the risks posed by the developments. “
She added, “It is well known that the British and Irish people of Shielddock commute back and forth across the North Sea every year, but this is the first published data about the specific routes they took, the time it takes for the migration to complete, and how fast the Shieldock fly is high.”
Four Shelduck is equipped with solar powered GPS-GSM tags, allowing BTO scientists to track their migratory movements in great detail and in near real time as GPS data is downloaded via mobile networks.
Incredibly, although the four birds have taken very different routes across the North Sea, they all have completed their migration in roughly the same place in the Dutch Wadden Sea. During the crossing, the birds flew at speeds of up to 55 knots, and up to 354 m above sea level.
The recorded movements indicated clear interactions with several wind farm sites, although most of these sites are still only in the planning stage.
Only one data fix was recorded within an operating wind farm when a bird flew inside the Egmond aan Zee wind farm.
This Shelduck plane was flying 85 meters, which could put her at risk of colliding with the wind farm’s rotating turbine blades, sweeping an area between 25 and 139 meters above sea level.
In fact, the majority of Shieldax’s four voyages occurred less than 150 meters above sea level, placing it in a “collision risk zone” for the many offshore wind farms that would otherwise pass through.
The BTO team plans to extend the tracking project and gather more data to verify whether Shelduck is really at risk of a collision, or whether residents can adapt to this basic renewable energy infrastructure.
“More work,” adds the research team, “is also required in labeling approaches in order to extend the propagation period beyond major moulting, and capture data on return relay. A larger sample size of tracked birds is needed before firm conclusions can be drawn on Shelduck migration.” Ideally, this would include birds of a wider geographic range than the British breeding sites, as well as the Sheldack that breed on the continent but migrate to Britain for the winter.