The late arrival of Bewick’s swans in the UK for winter could be linked to warmer weather, experts believe.
The first pair – whose appearance traditionally marks the start of winter – arrived at the Wildfowl & Wetland Trust’s Slimbridge Wetland Centre last week.
It is the latest the birds have arrived at the site in Gloucestershire since 1965.
Although the impact of the weather on bird migration is still being understood, it is thought likely the warmer climate is leading to the swans arriving later and in smaller numbers than in previous years.
The first Bewick’s to return this year were Fortune Two and Combo.
Fortune Two is aged 19 and first arrived as a cygnet at Slimbridge with his parents Sauber and Manero in the winter of 2003 and 2004.
He paired with Combo in the winter of 2005 and 2006 and they have returned every year since but have only managed to bring back cygnets once in 2013.
Dr Julia Newth, from the WWT, said: “The arrival of the Bewick’s swans this year is later than usual, it has been a mild autumn in the Arctic so the Bewick’s have left their breeding grounds later.
“The Arctic is warming twice as fast as the rest of the planet and there are significant changes happening on the breeding grounds.
“Although we don’t fully know the impacts yet, changes in the weather do influence migratory patterns.
“Migration patterns are changing in other ways too. The Bewick’s swans are not wintering as far west as they used to, and this is linked to the milder winters in Europe.
“The UK stronghold for these birds is in and around our wetland sites at WWT Slimbridge and WWT Welney with some around WWT Martin Mere.
“These wetland habitats are vitally important wintering grounds for these amazing birds.”
Bewick’s are small white swans with a black and yellow bill and every winter they return to the UK to escape the Arctic winters of Russia – travelling a 3,500km journey.
In 2020 a census yielded a total of 1,290 Bewick’s swans in the UK and Ireland, which represents a decline of 70% compared with the total recorded in 2015 of 4,392 birds.