DEFRA has urged extra vigilance for the signs of avian flu as 100s of thousands of migrating birds begin to return to Britain from Europe.

The highest risk is from birds that have passed through the Czech Republic, Germany and France, according to a risk assessment by DEFRA.

Last month there were three outbreaks of the H5N1 strain in the Czech Republic, three cases in Germany and one in France.

Veterinary experts do not yet know which bird species is spreading the virus but several species will move to Britain from infected areas in the next few weeks, a DEFRA spokesman said.

Up to100,000 pairs of Blackheaded gulls, returning from Baltic Sea have been named as the biggest and most imminent risk.

Then next month the risk increases again with 400,000 pairs of Mallard ducks expected to return from breeding grounds in Germany and the Czech Republic.

For our Special Report on Avian Flu click here