However, they have urged people to remain calm in light of the first case of bird flu in the UK as there is no indication the disease has yet spread to the domestic bird population.

NFUS Deputy Chief Executive James Withers said, “We will be liaising with the authorities to determine the veterinary advice on the next steps.

“It appears this finding has been in a wild bird, so there is no evidence yet it has reached the farmed population, and experience of cases elsewhere in Europe show there is no guarantee it will do so.

“Any poultry farmers in the immediate area should bring their poultry indoors and those outwith the 10km surveillance zone should prepare for a national order to do the same.

“We’re urging all our members to double-check the measures they have in place to prevent, as far as possible, contact between wild birds and farmed poultry.”

Mr Withers said, “The poultry industry has been preparing for this day, but it doesn’t make it any less worrying.

“We are working very closely with the Scottish Executive.”

An NFUS spokeswoman added the public should not be alarmed.

“Everything that can be done is being done.”

There are approximately 16 million poultry farmed in Scotland. The industry is worth around £110 million a year to the country’s economy.

Jim McLaren, vice-president of Scottish National Farmers’ Union, said Scotland was well-placed to prevent the disease spreading to farm birds.

“Many other countries in Europe have had experience of this problem in the last few months and the switchover from the wild bird population to the farm population has only happened, I think, in France and perhaps one other country.

“The UK has an excellent record on animal welfare and livestock husbandry, and I’m sure if the rest of Europe has managed to keep it out of their farm population to that extent, Scotland should be no different.

“In the poultry industry the birds are being watched on an hourly basis.

“Any premature bringing in of free-range birds would have a bigger welfare implication than indeed leaving them out in a low-risk spread situation,” he added.

NFU Scotland president John Kinnaird said it was good news the dead swan was thought to be native.

Speaking from the harbour in Cellardyke, he said, “It’s a mute swan, which is good because we know where all our native population of swans are. If it had come from abroad then migratory birds are much harder to track.

“There are nine poultry premises within 10km of here and all the farmers are extremely worried. They are keeping their chickens indoors and the rest of the country is getting ready to do the same.”

* Wildlife body RSPB Scotland plans to carry out daily checks for sick or dead birds on its east coast reserves. Staff have been carrying out twice-weekly checks since October but these will now take place daily at the society's Vane Farm, Loch of Kinnordy and Loch of Strathbeg reserves, it said.

* The Dunkeld-based representative of the UK’s largest shooting organisation has appealed for calm.

Dr Colin Shedden, Scotland director for the British Association for Shooting and Conservation, said there was no need for over-reaction.

BASC was co-ordinating a monitoring and testing scheme for ducks shot in Fife due to its high concentration of poultry farms, although Dr Shedden added this was “coincidental”.

“At this stage the impact on shooting will be those estates that fall within the protection zone. There’s very little that can be done at this stage but a few estates may be affected by the inability to bring in pheasants.”