Fears are growing that Britain could be hit by a bird flu outbreak after France confirmed its first case of the virus.
Bird flu spread westwards across Europe from Asia
Ministers have admitted the French case made it "likely" the disease would begin to affect birds in Britain.
The National Union of Farmers has also expressed worry over the development, with its poultry spokesman saying: "I'm more concerned than I was a week ago."
French officials have said a dead duck "probably" had the H5N1 strain, which has killed dozens of people in Asia.
Scientists are running tests on the wild duck, found near Lyon in south-east France, to find out if it was the deadly strain.
Charles Bourne, chairman of the NFU's poultry board, said it was a "good pointer" that no commercial birds had been affected in Europe.
But he said bird experts had "rather changed their tune".
"All the experts said the migratory birds wouldn't be bringing [bird flu] this way - they'd be taking it off to Siberia.
"So I can't pretend that I'm not more concerned than I was a week ago."
Fred Landeg, Britain's deputy chief veterinary officer, said there were "robust surveillance measures" in place and so far no H5N1 had been found in the UK.
"The expert ornithologists have advised that ducks from the Lyon region do not normally fly to the UK at this time of the year," he said.
But he added that the pochard duck used a migratory path which took it across Britain.
He said Defra would continue to monitor the situation and encouraged the public to report any unusual wild bird deaths.
The president of the British Veterinary Association, Dr Freda Scott Park, said people should report any dead birds to the Defra helpline.
'Not rocket science'
John Widdowson, from the British Free Range Egg Producers Association, said the government had done as much as it could to prepare for the spread of bird flu to the UK.
He said the most important thing now was to keep the disease out of poultry flocks.
A professor of virology at Queen Mary's School of Medicine in London, John Oxford, said farmers should protect their poultry immediately.
"It's not a question of wait and see. It's a question of taking action."
He said the virus would spread from wild birds to domestic ones by contact.
"What's the answer then? Stop the contact. That's not rocket science."
Bird flu expert Professor Hugh Pennington, from Aberdeen University, said although there was still doubt about whether bird flu would arrive in the UK, the country had to be "much better prepared".
"There is a reasonable chance that it will come here in wild birds.
"What we have to do is stop it getting into our poultry industry," he told BBC News 24.
"There is no real threat to the human population because this virus has not yet mutated and it may never mutate into a form which spreads from person to person."
Defra helpline is 08459 33 55 77