I believe Rufous is more likely than Allen's in Pleasant Hill. Allen's
prefers coastal fog. That said, the females are not distinguishable in the
field unless you can see the shape of the tail feathers. One thing I've
noticed about Allen's is they often have somewhat elongated pointed tails
vs. the more rounded tail tip of Rufous.

E.g. https://fog.ccsf.edu/~jmorlan/alhu1010372.htm

BTW a percentage of Rufous Hummingbirds have green backs, so that mark is
not 100% reliable unless the back is all red.

Another point is that in the Bay Area Allen's arrive and depart earlier.
Some arriving in late January and gone by the end of August. Rufous don't
usually arrive until late February or March. Females and immatures migrate
in the Fall in good numbers throughout the Bay Area with the vast majority
of Selasphorus seen after early September being Rufous. In both species
the adult males don't stay around in the summer for nesting. Rufous males
migrate south in the mountains and Allen's along the coast, both wintering
in Mexico.

Anyway, if you put these into eBird, it may be best to chose the
Allen's/Rufous category instead of assuming one or the other. This is
particularly true after September when eBird reviewers tend to filter any
claims of Allen's and ask for details.


On Sun, 29 Mar 2020 21:41:46 -0700, "Alan Bade" <alanbade@jps.net> wrote:

Hi folks- we had what I think might be an Allen's hummingbird at one of our feeders in southern Pleasant Hill. It was a female.Here's the ebird list with photos. https://ebird.org/checklist/S66386534

In one of my photos you can see a faint orange eyebrow which suggested to me an Allen's, as my Sibley guide calls out the orange eyebrow on the Allen's, but not the Rufous. But other photos don't show that much orange eyebrow.

--
Joseph Morlan, Pacifica, CA