Three correspondents suggested that this could be either a Rufous Hummingbird or an Allen's Hummingbird.

One commented: "I think it's the dreaded Rufous / Allen (Selasphorus sp.). In other words you can narrow it down to being either a Rufous or Allen's Hummingbird, but without birding superpowers can go no further. I suppose it's somewhat like seeing a fall, non-calling empidonax that you'd love to put a species name to, but realistically can't be 100% sure of it's ID. They (Arizona birders) actually just call them "Rufous Allen" and seemingly feel no guilt about it..."

Allen Chartier added: "This one looks like a female (age uncertain) Rufous Hummingbird. It is great that you have a shot of the spread tail, as that is a great way to distinguish Rufous from Allen's. But, the second rectrix (second out from center) does not show the distinctive "notch" that a Rufous would show. Many that I've banded have been similarly nondescript, and this may suggest it is an immature. I think it is a Rufous, though, because all the tail feathers appear relatively broad...they'd be narrower in Allen's, especially the outer one. I'm 95% sure of the ID, but not 100%."