This Cooper's has the barred rufous underparts of an adult, but its crown shows some retained juvenile streaking and its shade is lighter than the very dark gray of an adult. See also the photograph showing the rear dorsal view of this bird, with many retained juvenile brown feathers: http://www.pbase.com/image/145707713 . So it is evidently a year-old bird undergoing first prebasic molt. It was together with a juvenile Cooper's, and may have been one of that bird's parents; BNA Online reports breeding by some year-old immature birds of this species, and the Santa Clara County Breeding Bird Atlas reports a good number of immature birds among the nesters here.