The cause of the bird flu outbreak in Suffolk remains unknown but carriage by wild birds seems increasingly unlikely.
The RSPB is urging Defra to immediately put in place stringent measures to prevent wild birds picking up the virus from the farms where the disease was found.
Dr Mark Avery, Conservation Director, said: 'Defra must make sure there is absolutely no chance of the virus spreading into wild birds. It could still be there in the soil where birds like rooks, crows, starlings and pigeons could be foraging for food.
'It seems less and less likely that wild birds brought this disease here and Defra and the land owners must ensure that wild birds do not end up as victims of this outbreak.'
There are a number of measures necessary to minimise the chances of the bird flu virus surviving. These include disinfecting and ploughing land and keeping wild birds away from affected farms.
Dr Avery said: 'Efficient bird scaring is the key. It will not be enough to use deterrents that birds will quickly get used to.'