I recall someone, on a wildlife forum that I frequent, refer to Swallows as bullets with wings. Haha, I don't think they were far off with that reference, as I find it extremely challenging to get a sharp/in focus shot of them in flight. This is about as close as it gets for me, with my current equipment setup. At least bullets travel in a strait line. These small bird's flight pattern is quite erratic I find.
I don't know what species of bird this is (below).