I heard this story whilst on Fair Isle so thought I'd share it here. It goes like this, group of birders on Fair Isle claim a Blyth's Reed they get all excited and ring the obs and let them know, more people go and see the bird and confirm that it is indeed a Blyth's Reed, more people get excited but they soon realise that the bird doesn't look very well. But it's still a Blyth's Reed and are really excited. Deryk turns up looks in scope at said bird ''that's a Reed Warbler'' takes another look ''thats a dead Reed Warbler'' goes and picks bird up and proves it was indeed a Reed Warbler.
Morale of the story, don't think that any bird you have in the field is gonna be rare just because you're on Fair Isle and elsewhere always presume its the common alternative and prove it otherwise.