This presumed (western?) Willow Flycatcher was photographed at Daniel's Ranch, BBNP, Brewster county, Texas on September 04, 2011:
The general feel of the bird in the field was that of a rather brown Willow Flycatcher, but is the primary projection quite short, and the mandible has a dusky tip (?). It was not seen to vocalize.
It has a warmish tone to the uppertail coverts, a fairly strong yellow (tinged buff on sides) wash to the ventral flanks and vent. There is a paler partial collar sweeping up around the auricular.
These are all supposed features of White-throated Flycatcher E. albogularis. Click here to see a photos of White-throated Flycatcher. Another illustrated page about White-throated Flycatcher is here. So, can some forms of Willow Flycatcher have this suite of White-throated Flycatcher-like features? - I can find no reference to such individuals in my collection of literature:
Perhaps the only clear identifcation feature is voice - click here to listen to the distinctive vocalizations of White-throated Flycatcher .
NOTE: I found a bird quite similar to this individual on the same date but near the river on the eastern side of the Park: click here to see it.
NOTE: I found another bird similar to this individual on at Sam Nail Ranch, BBNP in the late Spring 2013: click here to see it.