Staff at a nature reserve in Suffolk are urging the government to test dead birds on the site for bird flu.
More than 38 birds have been found dead at RSPB Minsmere near Saxmundham and many others are said to be unwell.
Volunteers and staff members told ITV News that they are distressed by the number of dead birds they've seen in a week and concerned that the virus could spread.
Last Sunday, the first fifteen dead birds were found on the main area of the reserve and it was reported to the Department for Environment, Food and Rural Affairs (DEFRA).
Since then, the numbers have continued to rise.
Defra advised the reserve not to touch or remove the birds and so for now, the carcasses remain where they are in full view of the public.
David, a staff volunteer at RSPB Minsmere said: "Yesterday I had a count first thing in the morning of 38 but today I haven’t done another count today but I can see there are more than yesterday.
"Last thing when I left yesterday afternoon there were birds that were obviously very unwell.
"If the mortality were to take a big upwards movement, this could actually be tragic for some of the species here.”
So far, it’s black headed gulls, common and sandwich terns that have been affected.
It has happened during a very busy time as seabirds gather together on the scrape to nest and raise their young.
Nick Forster, Senior Site Manager at RSPB Minsmere said: "Dead birds lying out there will attract other creatures to eat them and that could include birds like Marsh harriers and red kites which we usually have on the site who may become infected again if it is avian influenza.
"We would like to be able to tidy up or Defra to tidy up but until we hear from them it is as you say a waiting game”
A spokesperson for Defra said that the deaths are currently under investigation and that a collection of some of the birds for testing will be arranged. In the meantime visitors are being advised not to approach any sick or dead birds.