It has been reported that nine dead swans have been tested positive for bird flu at Abbotsbury Swannery in Dorset.
The swannery was also hit by the virus in January 2008 when restrictions were put in place. A number of dead birds tested positive for the strain of the virus.
They said about 80 birds had died so far this winter when it would normally expect about 30 to 40. The cause of most of the swans' deaths is not known.
Tourism general manager John Houston said: "It is spread through bird droppings. It has been in Europe on a wide scale for the last few months so we have expected it because you can't stop migratory birds crossing from the continent.
"This time of the year is a very difficult time of year for wild birds anyway and we would normally expect to see 30 to 40 swan deaths over the winter period but, as of Saturday, we have had 80 so far which is above the norm and is distressing for the staff who are very close to these wonderful birds."
There are about 600 birds at the Dorset site, the world's only managed colony of nesting mute swans.
Restrictions have been put in place across the UK in a bid to halt the spread of the disease.
800,000 birds have been gassed in south west France because of the outbreak. In the UK the disease has been confirmed in locations including Yorkshire, Lincolnshire and Wales.
