So, in response to Bob's question of a few weeks back, now that H5N1 has been found in a British swan, the BBC has the answer:

What should I do if I see a dead bird?

Do not touch it. Government advice is that if you find one or more dead swans, ducks or geese, more than three dead birds of the same species or more than five dead birds of different species, in the same place, you should contact the Defra helpline on 08459 33 55 77.

So there you have it: clear and unambiguous advice. Not just who to call, but under what circumstances -- and it seems Bob, with just one dead bird, did exactly the right thing by not calling! Go him!

...of course, the nitpicker in me (and you lot. See, I know you) wants to point out that there is some ambiguity. "The same place" is slightly ambiguous, for a start. How big an area is a "place"? Within sight of each other seems reasonable, but what if they're scattered around a lake? The same county? Does "England" count as a place? It's also failed to specify the type of dead bird -- specifically, one that looks like it might have died of flu (whatever that looks like). For instance, if you work in a poultry slaughter facility, it would not be a good idea to go calling Defra in a panic the moment the plant kicks into action tomorrow. But the advice is good enough for people who are not grammar-analysing nerds (I assume such people must exist, though I don't know any myself).

(P.S. Poison update: less itchy today. Have also given up my vitamin supplements in case I'm overdosing or something.)