If it is a Great Crested Grebe, then determining the subspecies involved is essential: birds from sub-Saharan Africa are subtly different from those found in Europe, and have never been recorded north of the Sahara. Even a North African origin is highly unlikely: only a handful of Great Crested Grebes nest there. "The one thing that we can be sure of is that this grebe is very, very unlikely to be a migrant from sub-Saharan Africa." —Dr Richard Thomas, BirdLife International
Another vital clue is the age of the affected bird: if it was hatched in 2006, it indicates a local source of infection. Young grebes will only just have fledged and Great Crested Grebes are not migrating in early July. Indeed, birds in northern Spain are regarded as sedentary. However, some reports indicate the corpse was found six weeks ago: if true, then the bird must have been died sometime in May. "Perhaps the most likely explanation is that it was one of the scattering of wild birds killed by H5N1 this spring in Europe-possibly a bird that wintered in an affected part of the Mediterranean," Thomas added.
In February, a lorry load of 21 tonnes of illegally imported Chinese poultry meat was confiscated in Benidorm making it only a matter of time before H5N1 was reported in Spain unless the imports were prevented. "Perhaps H5N1 arrived in Spain the same way it got into Africa: in imported chicken products," said Thomas. "But even if it was smuggled in, it's difficult to see how it could have ended up in a grebe: it would be useful to know the circumstances under which the bird was discovered."