Government officials today confirmed that the H5N1 positive swan discovered in Cellardyke, Scotland was a whooper swan, not as previously thought a mute swan.

Initial identification had been hampered by the advanced state of decay of the carcass and the species was only confirmed through DNA profiling.

Whooper swans are migratory. The Icelandic breeding population winters in north-west Europe, including Britain and Ireland, the Low Countries and the Baltic. H5N1 has been confirmed in several whooper swans in the Baltic during February and March.

It seems plausible that the bird found in Scotland may have originated in this region and was attempting to migrate back to Iceland to breed, before becoming too sick to continue and alighting on the sea.

If this is the case, then it may be an isolated incident. However, it would be wise at this stage, not to dismiss the alternative theory that the swan was wintering in the UK (either in Fife or elsewhere) and contracted the virus locally from another species of waterfowl.

For this reason, the current restrictions should be kept in place and further surveillance of wild birds carried out.