When I saw this bird fly, I immediately thought it was a Sharpie from its small size and more rapid wing flaps than I'm used to seeing in a Cooper's. On examining the picture, the small head and forward wings, the eye centered on the head, the square tail, and the coarser streaks on the underparts all confirm the identification. This was the first Sharpie I had seen in many visits to Arastradero, where Cooper's are regular year-round.