Greetings All

Kevin Aanerud, who found the Empid in question, has identified it as a Least.
The short primary projection, relatively short triangular bill, some tendency
to flick wings, all fit with this diagnosis.

Addtionally, Least Flys winter rarely, but with some regularity, in CA. The
only other candidate, from above description, would be Dusky, which would be
almost equally as rare there during winter. A Dusky should have a longer and
relatively narrower bill than described and rarely flick their wings, though the
latter mark is a "soft" one.

Cheers
Steven Mlodinow