Mexican Jay Life History

Habitat

Mexican Jays inhabit woodlands of pine, oak, and juniper in the mountains of the southwestern U.S., from the edge of the desert to elevations as high as 7,000 feet (and over 11,000 feet in Mexico). They also live in desert grasslands, along stream corridors that have oak trees. Acorns form an important part of the diet, especially in winter, so they choose woodlands that have Arizona, Emory, Lacey, Grave’s, gray, red, silverleaf, and netleaf oaks in Arizona and New Mexico. In the Big Bend region of Texas where there are no Steller's Jays or Woodhouse’s Scrub-Jays to compete for food, Mexican Jays also favor woodlands with oaks but inhabit both higher- and lower-elevation habitats than in Arizona, including scrub woodland and coniferous forests. Other common tree species in the U.S. range of Mexican Jay include alligator juniper, Ashe’s juniper, southwestern white pine, ponderosa pine, Chihuahua pine, Apache pine, Texas pinyon, Coahuila fir, Douglas-fir, Arizona cypress, mountain mahogany, Texas pistache, and bigtooth maple.

Food

Mexican Jays eat mostly acorns and pine nuts in winter, and often store, or “cache,” acorns for later consumption. To eat acorns, they hold them with both feet on a perch and hammer them open with the bill. For pine nuts, they must find opened cones, usually on the ground, as their bills are not suited to prying seeds out of closed cones. In summer, they eat insects and other arthropods, snakes, lizards, frogs, and bird eggs and nestlings. In some winters, they eat small birds and mice. They forage in groups in trees and other vegetation, searching branches, trunks, and leaves for food, and also forage on the ground, moving leaf litter with the bill in search of acorns or invertebrates. On occasion, they capture winged insects in flight or remove prey trapped in spiderwebs, but they eat relatively few spiders. Beetles, bugs, cicadas, grasshoppers, crickets, dragonflies, butterflies, moths, and caterpillars are known prey items. Unlike many birds, they eat wooly bears and the hairy caterpillars of silver-spotted tiger moths, from which they remove the “hairs” before consuming. In spring and summer, they eat berries and sometimes visit agaves to drink nectar and eat insects.

Nesting

Nest Placement

Males often begin nest construction as part of courting females, usually well hidden in a tree, about 30 feet above the ground, near the trunk on a fork along a branch.

Nest Description

Male and female construct platform-like cup of sticks lined with rootlets, plant fibers, and/or animal hair. Nests average 13 inches across and 3 inches tall, with interior cup 5 inches across and 2 inches deep.

Nesting Facts

Behavior

Mexican Jays live in social groups that may be as small as five birds or as large as 25. In these groups, up to four females build nests and lay eggs. Normally, each female builds one nest and lays her eggs there (on rare occasions, several females lay in the same nest). In most cases, each female has a primary male partner that helps her guard the nest and seems to guard her as well. DNA research shows that these males are often not the biological father of the nestlings. Thus, both males and females mate with multiple members of the opposite sex. Beginning as early as late winter, males display to females by circling them, singing quietly, spreading the wings and tail, and often offering food. A male that mates with a female usually assists her in building a nest and stays near her, warding off advances of other males (often unsuccessfully). This male and female feed the nestlings, with help from many others in the group, including other males and nonbreeding birds, both younger and older. In one study, 40% of the young raised in one season were not the offspring of the primary male that fed them. After they fledge, the young continue to be fed by many members of the group—and typically remain with their group for the rest of their lives. Following the nesting season, there is no evidence that Mexican Jays maintain pair bonds, and males and females do not show a strong tendency to re-partner with their mate of the previous nesting season.

Conservation

Mexican Jay population trends have not been the subject of study, but in the United States their numbers appear to be stable. Partners in Flight estimates a global breeding population of 430,000 and rates the species a 13 out of 20 on the Continental Concern Score, indicating a species of relatively low conservation concern. Habitat loss is the chief threat to populations of this species throughout its range, as the forests they inhabit are under pressure from development projects and timber industries. Several studies have also documented mortality from grains containing fungicides and pesticides.

Credits

Li, S. H. and J. L. Brown. (1998). Do extra-pair fertilisations benefit female Mexican Jays? Ostrich 69:226.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

McCormack, J. E. and Jerram L. Brown. (2008). Mexican Jay (Aphelocoma wollweberi), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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