On Mon, 30 Mar 2020 11:01:52 -0700, mikeshannon@comcast.net wrote:

I am in Castro Valley, quite far from the fog and I am 100% certain that the hummers at my feeder are Allen’s. No doubt about it.

Yes, Allen's breed between the Bay up into the East Bay hills. They also
breed at Coyote Hills and I think there may be recent nesting records in
the Diablo Range which doesn't get much fog. Allen's are locally common
breeders in Santa Clara County but mostly on the west slopes of the Santa
Cruz Mountains where the fog creeps over the ridges. I think they are
generally very scarce east of the East Bay Hills.

But this is just for breeding. All these rules go away after the end of
August when migrant Rufous become fairly common throughout the Bay Area.

A recent paper studied the hybrid zone between Rufous and Allen's on the
north coast of California and into Oregon. It seems like these two
hybridize extensively there and act more like one species than two. I'm not
aware of any formal proposals to lump them yet, but stay tuned.

https://www.biotechniques.com/veterinary/scientists-discover-hummingbird-hybrid-zone/
--
Joseph Morlan, Pacifica, CA