Elizabeth,
I'm not an expert on hummingbirds by far, but since no one else seems to
be responding, here's a guess.
Based on the brownish color on the chest and sides and the portion of
the lower back that is visible, along with the stippling on the throat,
it's probably an Allen's or Rufous Hummingbird. I believe these two
species are the commonest winter strays in our area.
Allen's would be ruled out if the back is entirely or almost entirely
brownish. Otherwise, closeup pictures of the spread tail may be the only
way to distinguish the two.
I'm basing this entirely on information from field guides. I've seen
Allen's a few times in California, but have never seen a Rufous.
Jack Saba
Berwyn Heights Md