Social distancing
The UK’s largest breeding colony of Arctic terns has collapsed, and lockdown may be to blame.
Few aspects of life remain unaffected by coronavirus. In North Wales, the strange events of 2020 are believed to have led to the abandonment of the UK’s largest Arctic tern breeding colony. And scientists want the public’s help in working out where the birds have gone.
The Skerries – a group of islets lying off Anglesey – are host every year to thousands of Arctic terns. Normally, RSPB wardens would be on site to monitor the population and protect it from disturbance. But not this year.
In late May, Rachel Taylor, a senior ecologist with the BTO, received an email from an RSPB colleague who had gone to check on the colony and found just a handful of birds.
“He also saw a male peregrine sitting on the lighthouse as he arrived,” says Taylor. “They haven’t had a peregrine roosting on the lighthouse when it’s had wardens living in it. My guess is that, had the wardens been there, the terns wouldn’t have abandoned the island this year.”
But whatever the trigger for the exodus, it was a moment that Taylor was prepared for. Since 2012, she and her colleagues have been ringing 500 chicks a year on the islands. “We knew there was always a chance that the colony would collapse – it’s what seabird colonies do,” she says. “Every colony north of the Skerries has collapsed at some point and then subsequently recovered.”
The ringed birds would allow the team to establish where the birds go when disaster strikes. One Skerries bird has already been spotted with a large chick in Dublin Bay. Many others seem to have joined a colony at Cemlyn, around the coast from Anglesey.
About 80 per cent of the birds, though, are still unaccounted for. “There’s plenty we can learn from anyone who’s willing to look that little bit harder at terns’ legs,” says Taylor.
There is also the question of whether they will return. “When a colony recovers, is it because the same birds have come back? Or is it mostly young birds that didn’t go through the collapse event – effectively a new colony? The
next few years are going to be absolutely fascinating.”