I was sent some photos recently of an interesting bird in Europe as a potential vagrant Barn Swallow. I haven't spent much time looking at North American birds but the classic American seems to exhibit rusty underparts and an incomplete blue breast band. Some birds are not so rusty below such as this one below but the incomplete breast band is still a feature:
Then I stumbled upon Graham Catley's site and his photos of a very good looking bird. Was this in the UK this year as I don't recall mention of it?
What other features are there. I seem to recall length of tail streamers or is it tail spots?