Mexican Jays
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The Mexican Jay Aphelocoma ultramarina, also known as the Gray-breasted Jay, is a New World scrub jay native to the Sierra Madre Oriental and Sierra Madre Occidental mountains of Mexico, north to southeast Arizona, southwest New Mexico and westernmost Texas in the United States. Its preferred habitat is montane pine-oak forest in mountains.
It is a medium-large 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 similar, and juveniles differ only in the blue being grayer and less intense. The bill, eye and legs are black, except for juveniles, which may show a yellow base to the bill (see races, below). 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 diet consists mainly of acorns and pine nuts, which it stores in the autumn for use through the following winter and spring; excess stored seeds often germinate, thus perpetuating the bird's preferred habitat. Other food includes a wide variety of plant and animal matter, the latter including invertebrates, small amphibians and reptiles, and birds' eggs and nestlings.
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.
Subspecies
There are seven described subspecies that extend from the southern US into central Mexico. They are divided into three main groups: an eastern group in the Sierra Madre Oriental (including west Texas) where the juveniles have an all-black beak, a western group in the Sierra Madre Occidental (including Arizona and New Mexico) where the juveniles have a yellow base to the beak for up to two years, and a southern group in the Trans-Mexican volcanic belt of central Mexico where juveniles have a yellow base to the beak. In this last population, adults are larger and longer-tailed than those in the northern groups. The eastern and western groups might intergrade with one another throughout their U-shaped distribution in the Sierra Madres and Central Plateau. The southern group, on the other hand, is geographically isolated and likely more differentiated. Western races might also have a more complex social system and more cooperative breeding behaviour than the eastern races; the yellow in the bill may be related to this, in allowing the birds to determine each others' age and social status. Another difference is in egg color. Jays in the western group lay uniformly blue eggs without speckles while jays in the eastern group have been found to lay polymorphic eggs ranging from plain blue to blue with heavy speckling.
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Related Web Resources: USGS
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