In eastern Mexico, populations with longest wings and tails occur to the north; those with shortest wings and tails on Yucatán Peninsula. Variation in bill length parallels that in wing and tail length, except that individuals on Cozumel Island have very large bills relative to adjacent mainland populations. Ratio of bill length to wing length shows little geographic variation, except for Cozumel Island birds, which have high bill-to-wing ratios (Traylor 1979a).
Subspecies satrapa has a whiter throat and a paler, more yellowish chest, somewhat paler yellow underparts and a slightly paler gray crown than despotes and melancholicus, and is smaller than melancholicus (Cory and Hellmayr 1927, Stouffer and Chesser 1998). The color of the throat and chest of despotes is intermediate between those of satrapa and melancholicus. The underparts of despotes are yellower than those of satrapa, and despotes is smaller than melancholicus (Cory and Hellmayr 1927).
Kingbirds of the nominate subspecies breeding at south temperate latitudes of South America have longer wings than those of the same (nominate) subspecies breeding in the Amazon Basin (Jahn et al. 2010d).