Vets are investigating which birds need to be culled - and which could be spared - after an avian influenza outbreak at a treasured Norfolk wildlife haven.

Pensthorpe Natural Park, near Fakenham, was closed to visitors after a case of highly pathogenic bird flu was confirmed on Saturday.

As well as a breeding ground for many ducks and wading birds, the reserve also works on conservation projects for rare and protected species such as cranes, corncrakes and turtle doves.

Eastern Daily Press: Ducks and wading birds feeding at Pensthorpe Natural ParkDucks and wading birds feeding at Pensthorpe Natural Park (Image: (c) copyright newzulu.com)

Although it has not yet been confirmed which species are affected, Defra said "swift action" has been taken to limit the spread of the disease, and all infected birds will be humanely culled - along with birds in the same "epidemiological group".

But they said rare or endangered birds could be spared if they do not pose an animal health risk.

Their statement says: "We are currently assessing how many birds in the collection form part of the same epidemiological group as the infected birds and therefore need to be culled. We will inform the keeper of our decision as soon as possible.

"If there are birds that are rare or endangered species in the same epidemiological group and sparing them would not be an animal health risk, we will review whether a derogation from culling can be considered."

Christine Middlemiss, the UK's chief veterinary officer, said: “Any birds that have tested positive for bird flu will sadly need to be culled in order to limit the risk of the disease spreading to other birds and to mitigate any potential risk to public health, which remains low."

Health agencies advise that although avian influenza is devastating to bird flocks, the risk to human health and food safety is very low.

A statement issued by the park says the infection was most likely carried by wild birds flying into the reserve.

“The nature reserve has been liaising with leading organisations including Defra and, as the safety of our birds – and any birds outside the area – is paramount, the park will therefore remain closed for the time being, although we will be expecting to update on the investigation in the coming days," it says.

All captive birds, including commercial and pet poultry flocks, have been required to be kept indoors since an Avian Influenza Protection Zone (AIPZ) was enforced across the country in October.

It was implemented in a bid to contain the UK's largest-ever outbreak of bird flu - although the Pensthorpe case is only the third recorded so far in Norfolk this winter.

It follows outbreaks which prompted the culling of poultry at a farm at Pentney, near King's Lynn, and in a small domestic flock at a residential property on the Holkham estate.

Anyone who finds dead swans, geese or ducks or other wild birds should not touch them, but report them to the Defra helpline on 03459 33 55 77.