I learned that this is a Violet-Green Swallow. The Violet-Green Swallow has dark eyes mostly surrounded by white, Emerald green crown and back and glossy purple wings and rump. It is a gorgeous small bird That summers in the Northwest. As with all swallows, they are true expert aerialists, but without any tightrope or other apparatus. They perform their aerobatics in the open sky, like the barnstormers of old, as they feed on flying insects using acrobatic twists and turns. I was fortunate to see this one at rest in Delta Ponds, as they are usually on the move.