Luckily it was also seen by some birders far more expert than I. After a few days of review they decided it was not a Dusky Flycatcher, as first thought, but was in fact a Hammond's. For my two cents, the Hammond's do seem to be a bit more yellow than the Duskies, but that's something I can only tell from reviewing lots of photographs, not from field-obersvations alone.
The soft grays and yellows make for a beautiful and soft composition, one that seems unique to the Empidonax flycatchers (Warblers and Kingbirds being a stronger yellow). This Hammond's was another one of my favorite sightings on the BiF Tucson trip this February.
