A number of dead and distressed swans have been spotted on a city's river.
Toby Wood, from the Peterborough Civic Society, said seeing the birds on the River Nene at Fletton Quays was a "horrible sight".
"I've not seen anything like that in the city for several years," he said.
The Department for Environment, Food and Rural Affairs (Defra) said people should not touch dead wild birds, but should report them.
The country has been dealing with the largest outbreak of avian flu on record.
"It was a horrible sight really," said Mr Wood, who posted images of the birds and video of a live swan on social media on Thursday.
"I saw a swan obviously in distress, going round and round in a single circle," he said.
"Even the birds themselves looked a bit fed up and depressed and a bit disorientated."
In its advice about bird flu on its website, Defra states: "Our advice to the public is not to touch or pick up any dead or visibly sick birds that they find.
"The public are encouraged to report findings of a single dead bird of prey (including owls), three or more dead wild waterfowl (swans, geese or ducks) or gulls, or five or more dead birds of any species.
"We will then collect some of these birds and test them to help us understand what risk is posed to poultry and other captive birds."
Elsewhere in Cambridgeshire, extra bird flu restrictions have been put in place in locations including March, Soham, Somersham and Great Gidding.
The whole of G reat Britain was declared an Avian Influenza Prevention Zone (AIPZ) last month - this followed followed the imposition of similar measures in Norfolk, Suffolk and most of Essex introduced in September.
It means by law poultry businesses and pet owners must follow strict biosecurity rules, and in England all birds must be housed inside, Defra said.
The H5N1 strain of the avian influenza virus is highly contagious among birds, and spread by close contact with an infected bird, whether it is dead or alive.
Defra said the UK Health Security Agency advised "the risk to public health from the virus is very low".