'Swanfall' marks first cold snap
Dozens of Bewick's swans have flocked to Britain in a "swanfall" to mark the first cold snap of winter.
Eighty-one swans reached WWT Slimbridge in Gloucestershire after completing their 2,500-mile journey from the Arctic tundra.
The birds migrated to the centre during recent cold, clear nights, doubling the size of the roost there.
The arrival of so many swans in this way - dubbed a "swanfall" - generally coincides with the first cold snap in winter, as the birds seek ice-free wetlands.
This year, two swans and two cygnets were the first to reach the centre on November 6 - the latest arrival since 1969.
Their visit traditionally heralds the beginning of winter and was around two weeks late, with many birds choosing to remain as far east as Estonia due to mild weather.
WWT Wildlife Health Research Officer, Julia Newth, helps to conserve Bewick's swans, which have been in decline since the 1990s.
"The arrival of lots of Bewick's swans is a traditional harbinger of cold weather and it feels truly wintry here at WWT Slimbridge with crisp, clear days and hundreds of swans crowding onto the lake at dusk," she said.
"It's been a fantastic spectacle for everyone who's visited over the Christmas break.
"Sadly, there's a serious side and the number of Bewick's swans in Europe has dropped by over a third, but we're doing all we can to get to the bottom of the problem and everyone who visits is supporting the conservation of these beautiful wild birds."
Bewick's swans fly from their breeding ground in the Arctic tundra to Britain to rest and feed over winter, before they head back ahead of spring.
They are loyal to their winter sites, so the same ones return to WWT Slimbridge every year.
Experts at WWT identify Bewick's swans by their unique bill patterns, a method started 50 years ago when artist and naturalist Sir Peter Scott first recorded the facial marking of the birds at Slimbridge.
The work is now one of the most intensive single-species studies in the world and has recorded in detail the lives of nearly 10,000 individual swans.
Peak numbers of Bewick's swans at the centre usually reach more than 300.