See my other posting for a comparison to the similar Dusky Flycatcher. This Hammond's Flycatcher actually did vocalize which helped to clinch the ID. Some other key hints: more peaked looking head, long primary projection (how much the primary wing feathers project from the secondary ones), it stayed fairly high up most of the time choosing fairly mature deciduous and coniferous trees and finally it was in an area where other experts have regularly reported this species and not the other. This was in Ramsey Canyon in a comparatively more lush landscape with plenty of large trees including very large conifers. Of course taking photos of a small flycatcher in a conifer is not easy so luckily this one forayed a bit into nearby deciduous trees that had lost their leaves or dead branches.