Odd Sørensen discovered this dead whooper swan on 10 April. The Norwegian Food Safety Authority has received daily reports of dead birds and are asking the public to help report bird mortality in particular with ducks, geese, swans, seagulls, eagles, buzzards, crowd and ravens.

Knut-André Haugen found two dead swans with their heads under their wings outside Fredrikstad. Now the Norwegian Food Safety Authority suspects further spread of bird flu.

Bird flu, or avian influenza, has struck the Swedish poultry industry hard this winter. Since November, thousands of turkeys and more than one million chickens have been culled. Malin Grant, an epidemiologist at the National Veterinary Institute, says the virus can be deadly for domestic poultry but the strains currently circulating don't easily infect or spread between people.

The particularly dangerous strain of avian influenza virus H5N8 has been detected in a mute swan found on the Kopli peninsula in Tallinn.

Many of the dead seals that washed ashore in northern New England in the past few weeks tested positive for either avian influenza or phocine distemper virus, but it is still too soon to say if those viruses are the primary causes of the unusual die-off.