It Was a Buff-breasted Flycatcher

The last photo showed the all yellow-orange lower mandible – with no contrasting tip – as well as the relative lack of contrast in the face, throat, and head. True, this bird isn't very buffy, nor is the eye-ring very pronounced. These features are more obvious in the early fall after they've freshly molted.

One guess was Hammond's Flycatcher, and I just happen to have a photo of one of those taken on the same walk in Sawmill Canyon, below. Notice the contrast and the color of the lower mandible.