How cool they fly

House martins are practising in the courtyard today. They dive in from the side, right down to a few inches above the gravel, shoot along between the house and the linden trees, then pull up in a silently cutting curve and disappear over the top of the last tree.
Like teenagers in a half pipe.
I have opened the window to hear their chatter. Sometimes they assemble in one of the trees and they talk and talk and talk. Sometimes one of them flies straight into my room, does a mid flight about turn and accelerates back out again. I wonder if they know how cool they fly.
Let's assume they do.