Only seven Bewick's swans have been seen at the wildfowl centre
A Bewick's swan has astounded wildlife staff by returning to a Lancashire wetlands area 18 years after it was first ringed at the centre.
Staff at Martin Mere Wildfowl and Wetlands Trust (WWT) centre in Burscough also believe that the male swan may be at least 23-years-old.
The centre has only seen seven Bewick's swans so far this winter, the lowest number it has recorded since 1975.
The decrease has been attributed to an increase in temperature.
The birds now tend to spend the winter in Holland or on the east coast of England, the centre said.
Wardens at the centre believe the Bewick's swan will have travelled at least 100,000 miles so far in its migration journey from Siberia to winter in the UK, in its unusually long life.
Andy Wooldridge, Martin Mere WWT centre manager, said: "The Bewick's swan arrived back at Martin Mere on 6 January and after reading the metal ring number we were amazed to discover that the bird was ringed at Martin Mere as an adult in 1991, when we assumed he was at least 4 years old, making him an astonishing 23-years-old in 2009.
"Throughout his life he has been logged in the Netherlands and in Denmark, but was last seen in the local area in January 2006 by a former warden at Martin Mere."
The WWT centre also is looking after a baby beaver, called a kit, thought to be the first hand-reared in the UK.
The six-month-old beaver was found with serious injuries when he was just weeks old.
The kit is the offspring of TV stars Twiggy and Woody, who starred in the BBC's Autumnwatch programme in 2007.