Habitat
Subtropical and tropical lowland and montane moist forest, lowland dry and moist shrubland, high altitude shrubland, dry savanna, urban areas. From sea-level - 3,000 m.
Cassin's Kingbird (Tyrannus vociferans) [XC628240]
by Richard E. Webster from Carlisle Canyon, Grant County, New Mexico, United States (call, interaction calls)
Cassin's Kingbird (Tyrannus vociferans) [XC640583]
by Manuel Grosselet from San Lorenzo Cacaotepec, San Lorenzo Cacaotepec, Oaxaca, Mexico (call)
Subspecies
Closest relatives of genus may be Empidonomus and Tyrannopsis. Recent molecular-sequence data indicate present genus is monophyletic and sister-group to clade that includes Empidonomus and Griseotyrannus. There are two main clades within genus, loosely corresponding to "tropical species assemblage" and combination of "W" and "E" species groups of earlier authors, but with some exceptions. Phylogenetic analyses indicate that present species is basal to a clade including Western Kingbird (Tyrannus verticalis) and Scissor-tailed Flycatcher (Tyrannus forficatus) within an "eastern and western species group" that also includes Eastern Kingbird (Tyrannus tyrannus) and perhaps Loggerhead Kingbird (Tyrannus caudifasciatus) and/or Giant Kingbird (Tyrannus cubensis). On basis of similarities in voice and some aspects of behaviour, may be closest to Couch's Kingbird (Tyrannus couchii), Thick-billed Kingbird (Tyrannus crassirostris) and Western Kingbird (Tyrannus verticalis), but this not yet supported by molecular data. Validity of subspecies xenopterus questionable. Further research is required.
The following 2 subspecies are recognised:
vociferans Swainson, 1826 - Western and central USA (south-eastern Montana, eastern Wyoming, south-western South Dakota, south-western Nebraska, central and southern California, extreme south-eastern Nevada, southern Utah, south-western and south-central Colorado, northern and eastern Arizona, New Mexico, western Texas), Mexico (Baja California, and southern from western Sonora and Chihuahua to Oaxaca and Chiapas) and Guatemala.
xenopterus Griscom, 1934 - South-western Mexico (highlands of Guerrero).
BirdLife International Species Factsheet