Cassin's kingbird Tyrannus vociferans

Fairly large yellow-bellied flycatcher of the southwest U.S. and western Mexico. Dark gray head contrasts with white mustache. Also note blackish tail with white tip (but this can be difficult to see, especially when worn). Found in open, arid habitats with tall shrubs and trees, sometimes venturing up into clearings and meadows in mountains. Most similar to Western Kingbird, which is paler and less contrasting on the head. Listen for burry “ch-breer” calls.