This bird sang repeatedly from the tops of several tall conifers in the meadow north of Yuba Pass summit, and this habitat preference plus the small size of the bill support identification as Hammond's. But Dusky Flycatcher is also common at Yuba Pass, and I wasn't able to exclude Dusky as a possible identification of this bird. Comments welcome!

I took this photo at a considerable distance using stacked 1.4x and 2x teleconverters on my 500 mm lens.