The Mexican Jay, Aphelocoma wollweberi, formerly known as the Gray-breasted Jay, is a New World jay native to the Sierra Madre Oriental, Sierra Madre Occidental, and Central Plateau of Mexico. It reaches north to eastern Arizona, western New Mexico and western Texas in the United States. Its preferred habitat is montane pine-oak forest.
Note, in May 2011, the American Ornithologists' Union voted to split the Mexican Jay into two species, one retaining the common name Mexican Jay and one called the Transvolcanic Jay (see below).
The Mexican Jay is a medium-large (~120 g) passerine similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, and pale gray breast and underparts.
The sexes are morphologically similar, and juveniles differ only in having less blue coloration and, in some populations, a pink/pale (instead of black) bill that progressively becomes more black with age (Brown and Horvath 1989). Some field guides misreport this color as yellow because the pale bill becomes yellow in museum study skins. The iris is brown and legs are black. It is most readily distinguished from the similar Western 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 Western Scrub-Jays, but, where they co-occur, the two species seem to show ecological and morphological character displacement (Curry et al. 2002).
In the winter, the Mexican Jay's diet consists mainly of acorns and pine nuts, which are stored in the autumn. However, they are omnivorous in all seasons and their diet includes a wide variety of plant and animal matter, including invertebrates, small amphibians and reptiles, and birds' eggs and nestlings (McCormack and Brown 2008).