A new study led by the British Trust for Ornithology in Scotland (BTO Scotland) has unveiled the migration routes and wintering grounds of one of Scotland’s rarest and most endangered seabirds – the Arctic Skua.
According to BTO Scotland, the discoveries are a crucial step towards understanding the threats the seabirds encounter when they are far from Scotland’s shores, and the steps needed to take to conserve them.
Arctic Skuas feed by stealing from other seabirds, which they relentlessly harass with remarkable agility and grace. Pursuing smaller species such as Puffins, terns and Kittiwakes, the 'oceanic pirates' do not give up until their chosen victim has either surrendered a beak full of seafood or disgorged the fishy contents of their stomach.
Yet despite their apparent invincibility, Arctic Skuas are the fastest declining seabirds in the UK, with losses of up to 80% in the breeding population since 1986.
The decline has led to Arctic Skuas being Red-listed as a Bird of Conservation Concern in the UK. Similar trends have been documented elsewhere in Europe, and Arctic Skuas are also classified as Vulnerable on the IUCN European Red List.
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Scientists from BTO Scotland have been trying to better understand their movements and conservation needs through fitting miniature, long-term tracking devices to individuals nesting on Fair Isle in Shetland and Rousay in Orkney.
The work revealed that skuas from both Fair Isle and Rousay, which are no further than 90 km apart, wintered thousands of kilometres away from one another. Some migrated to the Canary Current off West Africa, while most travelled further into the Southern Hemisphere, wintering off south-west Africa or south-east South America – covering distances of over 10,000 km.
The study also mapped the routes taken by the skuas during their long migrations and pinpointed crucial refuelling areas where birds stopped to rest and feed during their journeys.
After departing their breeding colonies in autumn, most Arctic Skuas headed south through the North Sea and English Channel, continuing along the Iberian Peninsula before heading south further still. In contrast, during spring migration, the skuas all converged on an important feeding hotspot in the mid-North Atlantic Ocean, where they could feed up ready for the upcoming breeding season back in Scotland.
Dr Nina O’Hanlon, Senior Research Ecologist at BTO Scotland, said: "By identifying where these wide-ranging seabirds spend their time away from Scotland, we can begin to uncover the threats they may face, and how these may impact the skuas’ survival and future breeding success.
“This knowledge allows us to prioritise future research and conservation actions to protect this charismatic seabird”.
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