The hummingbird spent a few minutes preening, so I took several pictures from different angles. Here's one showing a bit more of the throat:
And one with the tail spread, a valuable view for this species:
Unfortunately, having moved from the East Coast, I don't have a lot of experience with this group of hummingbirds. It's either a Rufous or Allen's Hummingbird. The Birds of North America account gives some indication of how difficult it can be to tell them apart: "Female and immature Allen's are, in most circumstances, impossible to distinguish in the field from female and immature Rufous Hummingbirds."
So perhaps I'm crazy to try! Feel free to chime in if you have thoughts about the identity of this bird. No matter what species it is, it still leads to useful hints about things to look for in the field, and some interesting insight into hummingbird behavior/migration.
I'm guessing that this is an adult female (correct me if you think otherwise!). There's a relatively distinct throat patch, and the central tail feathers appear to be mostly green (see below).
One of the most useful characters for separating Rufous and Allen's hummingbirds is the width of the outermost tail feather. In this case, I felt that that outermost tail feather was relatively broad, so I started leaning towards this being a Rufous Hummingbird (Selasphorus rufus). Here's the tail feather photo again:
Rufous Hummingbirds generally nest further north (as far north as Alaska) — although it sounds like knowledge of their breeding distribution in this part of California is somewhat uncertain due to the difficulty of separating them from Allen's Hummingbirds. They depart their more northerly breeding grounds in mid-June and early July and southbound migrants may start to appear at latitudes similar to this in mid-late July (right now!). They'll winter further south, in southern California and Mexico.
I was grateful for such an intriguing visitor, and I look forward to any comments you might have about its identity.