Whooper swans settle in Norfolk every winter
A record number of whooper swans migrated to the Fens on the Norfolk border this winter, up by nearly 50%.
Out of 13,000 swans counted by the WWT at Welney and the RSPB, whooper swans accounted for 7,296 of the total - far higher than the 5,000 normally seen.
Reasons could be down to the Fens seeing less snowfall than other parts of the country during December.
"Severe weather elsewhere in the UK may have pushed the whoopers further south and east," said WWT warden Jon Smith.
"A swan with a identification ring CHZ, which normally winters in Ireland, dropped in to WWT Welney for the swan feeds; there may well be many more swans in similar situations," he added.
Thousands of birds from the Arctic, including Iceland, Scandinavia and Russia, often migrate to Norfolk during the winter months, as the rural areas provide good sources of food and are safe from many predators.
"The wetlands in this area are incredibly important to these birds for roosting and the surrounding arable land provides a much needed food source in the form of waste potatoes, grain and sugar beets tops from the recent harvest," said Mike Burdekin from the RSPB.
A small number of this year's flock, which also included thousands of bewick's swans, have been ringed and will be tracked to record their flight behaviour.