Taken today, north of Santa Rosa, CA -- about 60 mi NW of San Francisco. It was attracted to some bird seed I was tossing out. My best guess (which is about worthless as I'm in preschool as a birder) is a Hermit Thrush. Didn't hear any calls. It was just about the same size as some Golden-crowned Sparrows that were also scarfing up the seeds.
Never seen one of these Diane it's a good shot. I have never seen a hermit thrush either but generally speaking I think you may well find a clue in the bill - sparrows are seed eaters hence the heavy based stronger bill, thrushes tend to have slimmer bills primarily for insects and snails etc as opposed to crunching seeds.