Couch's Kingbird (Tyrannus couchii) - HBW 9, p. 420

Taxonomy: Tyrannus couchii S. F. Baird, 1858, Nuevo León and San Diego, Nuevo León, Mexico.
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; two main clades within genus, loosely corresponding to “tropical species assemblage” and combination of “W” & “E” species groups of earlier authors, but with some exceptions. Present species formerly treated as conspecific with T. melancholicus owing to limited hybridization in Mexico (S Veracruz, Atlantic slope of N Oaxaca), and possibly intergrades with it, but differs significantly in voice. Furthermore, recent molecular data indicate that these two are not each other’s closest relatives, but that present species is part of a clade within the “tropical assemblage” that also includes T. albogularis and T. savana, although relationships among these three remain uncertain. Has been suggested, on basis of similarities in voice and certain aspects of behaviour, that this species may be closest to T. vociferans, T. crassirostris and T. verticalis, although this not supported by molecular data. Finally, probable hybrid with T. forficatus reported from New York (USA). N birds said to have longer wing and those from Yucatán Peninsula (proposed as race chloronotus) have longer bill than individuals from Guatemala and Belize, but differences insufficient to warrant naming of geographical races. Monotypic.