Wild speculation over “bird flu”

A whooper swan carrying the H5N1 strain is creating a lot of headlines in the UK. Initially I wondered why it took DNA testing to identify the bird – turns out that it was headless and badly decomposed.
The fact that this is a migratory species has led to several sources suggesting that it contracted the strain outside the UK and died during migration. Where exactly is the evidence for this? It rather smacks of an attempt to reassure the public that H5N1 isn’t rife in the wild birds of the UK. Isn’t it obvious that high density, intensively-farmed birds are the problem here, rather than wild birds?