Birds

The migration routes of one of the UK’s largest ducks were first revealed, but much still remains a mystery

New research, just published in Ringing & Migration (https://doi.org/10.1080/03078698.2019.1887670), has used cutting-edge tracking technology to examine how one of the UK’s largest ducks, the Shelduck, interacts with offshore Wind turbines during their migration across the North Sea.Your results show for the first time the length, speed and altitude of this journey.

Offshore wind farms are an integral part of many governments’ strategies to reduce CO2 emissions and mitigate the effects of climate change. However, it is important to understand how they can affect wildlife. The risk of collision with wind turbines is a particular problem for migratory bird species that travel across the sea, and there is also a potential increase in energy costs when wind farms act as a barrier for migratory birds. The majority of the British and Irish Shelduck go through a “moulting migration” to the Wadden Sea, which runs along the coasts of the Netherlands, Germany and Denmark. They make this trip in late summer every year after they finish breeding. There they replace their old and worn feathers and become flightless in the relative safety offered by the Wadden Sea before returning to Britain after their moulting is complete. However, on the way to and from the Wadden Sea, Shelduck has to cross the North Sea and navigate the growing number of wind farms along the way.

Shelducks, copyright Glyn Sellors, from the Surfbirds Galleries

Scientists from the British Trust for Ornithology (BTO) used state-of-the-art tags to track four Shelduck from the Alde-Ore Estuary Special Protection Area on the Suffolk coast to the Wadden Sea. Each bird took a separate route across the North Sea and used previously unreported stops in the Dutch Wadden Sea before continuing to moult in the Heligoland Bay off the coast of Germany. Interestingly, one bird moved back and forth between the Dutch and German Wadden Sea four times, adding an additional 1,000 km to its train journey. The reasons for this remain a mystery.

Ros Green, Research Ecologist at BTO and lead author of the paper, said, “Understanding the migration of species is an essential first step in understanding the risks offshore wind farms can pose to populations of Shelduck and other species. In addition, our tags provided data on Shelduck’s airspeed and altitude and provided additional important information on the extent of the risks arising from developments. “

She added: “The British and Irish Shelduck populations are known to move back and forth across the North Sea each year. However, this is the first published data on the specific routes, how long it takes to migrate and how fast and high Shelduck fly. “

The four Shelduck were equipped with solar-powered GPS-GSM tags, which BTO scientists can use to track their migration movements in detail and in near real-time, while the GPS data is downloaded via cellular networks. Incredibly, although all four birds took very different routes across the North Sea, they all ended their migration at almost exactly the same point in the Dutch Wadden Sea. During the crossing, the birds flew at a speed of up to 55 knots and up to 354 m above the sea surface.

The recorded movements showed obvious interactions with several wind farm locations, although most are currently only in the planning phase. Only one data fix was recorded within an operational wind farm when a bird flew inside the Egmond aan Zee wind farm. This shelduck flew at a height of 85 m, which creates a risk of collision with the rotating turbine blades of the wind farm, which sweep an area between 25 and 139 m above sea level. In fact, the majority of the flight of the four Shelducks took place below 150 m above sea level, which would put them in the “collision risk zone” of many offshore wind farms that they might pass through. The BTO team plans to expand the tracking project and collect more data to investigate whether Shelduck is actually at risk of collision or whether the population can adapt to this vital renewable energy infrastructure. “Further work,” adds the research team, “is also needed for tagging approaches to extend deployment times beyond the main moults and to collect data on return migration.” A larger sample of tracked birds is required before definitive conclusions about Shelduck migration can be drawn. Ideally, this would include birds from a wider geographic area of ​​British breeding grounds, as well as Shelduck that breed on the continent but migrate to the UK for the winter. “

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