Small bird, shiny dark blue back, and yellow breast. Distinguishable by the very forked tail when in flight(see second photo bottom left corner). Sited in abundance in union bay natural area between the shores of lake washington and the shore of one of the ponds, also in the group of birds were many violet green swallows. It was impossible to catch one of these birds not in flight, it seemed to be all they did, flying down very close to the water of the pond, steep ascents into the air followed by dives back down, occasional flocking, and generally flying all over the place.
If you think this observation is inaccurate, please add an ID, participate in the quality assessment above, or describe the inaccuracy in a comment.