Marked differences in size, color, vocalizations, and genetics have led some authors to consider at least two of these groups as separate species (Eastern and Western; Navarro-Sigüenza and Peterson 2004).

Western group Sierra Madre Occidental in northern [Jalisco] north to central Arizona and southwestern New Mexico.

Eastern group Sierra Madre Oriental in Nuevo León and western Tamaulipas north to Texas (Chisos Mountains).

Juveniles have an all-black exterior to the bill after fledging, but roof of inner upper mandible can remain partially white for up to two years.

Reports of less social behavior compared to other groups are over-stated and credible accounts of cooperative breeding (Ligon and Husar 1974) and large flock sizes (Bhagabati and Horvath 2006) exist.

It is most readily distinguished from the similar Woodhouse's scrub-jay by the plain (unstreaked) throat and breast, and the mantle contrasting less with the head and wings.

Its range somewhat overlaps with the Woodhouse's scrub-jay, but, where they co-occur, the two species seem to show ecological and morphological character displacement (Curry et al. 2002).

It has a cooperative breeding system similar to that of the related Florida scrub-jay, with several birds helping at a nest; these "helpers" are usually immature offspring of the dominant pair from the previous 1–2 years, but also include apparently unrelated flock members.