We have four species of swallows over the field right now. The deeply forked tail of the barn swallow makes them easy. The color of the violet green helps with that species. Tree swallows have a steely blue back, except in their first year. This swallow did not have the circling flight of a tree swallow and when it landed next to a tree swallow I could see it was appreciably smaller. After it flew some more and I saw the drawback of the wings it was clear that it was a rough wing. Now I want to see a bank swallow to round out the day.