Saw this bird while getting in the car, and thought it looked like Field Sparrow. I went back to get binos and camera and eventually re-found and photographed. Bird was not seen again on weekend. It was, surprisingly, with a Clay-colored Sparrow. If accepted, this is a first San Mateo County Record. Small size, with long skinny tail. Very brightly colored on upperparts and wings, lots of cinnamon tones and very bold white wing bars. Head showed bold white eyering, and gray background color with pale rusty on crown and post-ocular stripe. Small and bright pink bill. No streaking on pale gray-white underparts. No calls heard. Photos show contrast with older wing and much newer and fresher coverts and tertials. This suggests it is a bird from last season, so an immature (SY in banding terms).