Flycatcher, Empidonax difficilis
The "Western" Flycatchers (Pacific-slope and Cordilleran) are distinguished by the teardrop-shaped eye-ring, and by underparts that are yellower than those of other Empidonax flycatchers that pass through the SF Bay Area. The Pacific-slope is the only Empidonax that nests here, and hearing a "Western" give its high, clear upswept whistle note, which is joined to other sounds to make its song, supports identifying it to species, as does evidence that it is nesting. I was drawn to photograph the bird shown above and in the two pictures immediately below by hearing its call in July, a date that was likelier for a nesting bird than for a migrant.
This Pacific-slope Flycatcher announced himself by giving the upswept whistle note,
also, like the one shown above, in July, the nesting season. He may have nested
in Frenchman's Park, not far from my house -- though I did not see or hear him again
after the day on which I photographed him. He has a more classic "teardrop" than
the first bird shown, as does the bird shown below.
I did not hear the bird shown above and below vocalize, and I photographed
in late September, a date consistent with its being in migration. As Cordilleran
Flycatchers can't be distinguished from Pacific-slopes by plumage, a silent
"Western" type of flycatcher in migration season can't strictly be assigned
to one or the other of the two species. We don't know if Cordillerans migrate
through our area, but migrating "Westerns" here seem more likely to
be Pacific-slope, which breed north of us along the coast, so I've included it
here, with this caveat.