Song Sparrow - California Subspecies

I took these pictures of a Song Sparrow in San Francisco on May 2. I noticed that it was a little different than the Song Sparrows I am used to seeing here in Oregon, but I wasn't aware of the breath of subspecies identified. Some 52 subspecies have been named, however only 24 are currently actually recognized.
This Song Sparrow, I believe, belongs to the California group of six subspecies. I haven't figured out which yet, but I'll keep working on it. While there is a fair amount written about the various subspecies online, I found few pictures to help me. It's clear though, that this sparrow has darker and more crisply defined stripes on its breast and throat. If anyone is an expert, I'd love for you to point me to where I can find out more about this topic.