Officially speaking, this hummer will likely be a mystery forever unless we collect some DNA or get some exhaustive in-the-hand measurements.
Comments suggesting Anna's and Black-chinned Hummingbird were spot-on. But it's not quite right for either. In fact, it appears to be an Anna's x Black-chinned Hummingbird hybrid, the first reported such combination since a bird was collected in Santa Barbara, California in 1883.
The bird looks mostly like Anna's – rather chunky, thick-necked, shortish billed, and very dingy below. But the gorget is squared off lacking the flanges, and it lacks iridescence on the crown and behind the eye. I think the tail is too pointy for Anna's as well, and the bill may be a bit too long. The shapes of the primaries are more like Black-chinned – pointier and narrow inner primaries, and with larger, more bowed out primaries (better visible in the photo from my previous post).
Most striking however, visible only in this one photo below, is the color of the throat – a deep rose-purple, rather intermediate between the two. (And with a flash, it's not quite a perfect reproduction.)
I also got some recordings, which I uploaded to Xeno-canto.org. They don't have categories for hybrids, so I uploaded each cut that I isolated twice – once for Black-chinned and once for Anna's, and made a note in the comments. Here's the best one below, starting with a scold and ending with some of the call notes, which sound like a dull, heavy Black-chinned – again, essentially intermediate.