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The Pinyon Jay is named for its coevolved mutualism with pinyon pines of western North America (genus Pinus, subgenus Strobus, subsection Cembroides; 1). Also known colloquially as the “piñonero” and “blue crow,” the Pinyon Jay serves these pines as the primary long-distance disperser of their large, wingless seeds. In a mast year, Pinyon Jays in turn reap the reward of an abundant food source rich in energy and nutrients.
The Pinyon Jay is a highly social, cooperatively breeding bird of the foothills and lower mountain slopes of the western United States and northern Baja California, Mexico. Although omnivorous, it is committed to the harvest, transport, caching, and later retrieval of pine seeds, aided by a relatively long, strong bill; an expandable esophagus; and long, strong wings. Individuals have excellent spatial memories that allow them uncanny recovery accuracy when digging up their hidden food stores months after caching, even through snow.
Social organization is complex. In the 1970s, winter flocks ranged from 150‒250 (2) with anecdotal reports of more than 500 birds, but more recent reports indicate most flocks with fewer than 100 birds (eBird). Many birds spend their entire lives in their natal flocks. Individuals that do disperse—mostly females before they are one year of age—generally travel short distances. Birds may live up to 16 years in the wild and captivity. Although permanent residents, in years when cone crops fail, individuals may disperse far from their very large home ranges, making them one of the irruptive species of North American birds.
Where abundant crops of pine seeds were cached the previous autumn, the Pinyon Jay, one of the earliest nesting passerines in the United States, may begin nesting in the cold of winter. It nests synchronously in loose colonies of tens of hectares in area. Nests are bulky and well insulated and often are placed on the south side of tree foliage—usually one nest to a tree and scattered throughout a traditional breeding ground. Autumnal breeding by this species occurs in a single population in central New Mexico, when crops of pinyon pine cones are large. Physiologically, the presence of pine seeds and green cones reverses gonadal regression and stimulates testis growth in wild and experimental birds, which triggers breeding (3, 4).
At some nests, yearling males help provision their younger siblings. Young from multiple nests gather in crèches, where they are fed predominantly by their parents; this requires exacting individual recognition. In these crèches, young birds preen each other, exert dominance over their associates, and are subject to severe predation.
The Breeding Bird Survey has documented that the Pinyon Jay population has been declining rangewide for over 50 years (5). As a result, the Pinyon Jay is listed as Vulnerable by BirdLife International and is recognized by several state and federal agencies as a species of conservation concern. The impacts to this species are both historical and current. In the 1800s, silver mining in Nevada consumed vast acreages of pinyon–juniper woodland for mine construction, charcoal for smelting, and associated uses (6). In the latter half of the twentieth century, federal and state government agencies cleared an estimated three million acres of this habitat of trees to create grazing land for cattle (6). Currently, the greatest threat to Pinyon Jays is probably climate change, with documented climate impacts including widespread mortality and morbidity (7, 8), reduced cone crops (9, 10), and decreases in canopy cover (11) of pinyon pines. Current management practices, such as extensive woodland thinning for fuels reduction and to create habitat for other species such as Greater Sage-Grouse, are additional impacts.
Most of what is known about this bird comes from the southern part of its range. R. P. Balda, his students, members of his family, and a local amateur (Gene Foster) studied social behavior and reproductive success in a color-banded flock (hereafter, the Town Flock), in and around Flagstaff, Arizona, for more than 18 years (documented in 2). In addition, J. D. Ligon and his students at the University of New Mexico provided information on the species’ mutualism with pinyon pines, vocalizations, and mate choice. More recently, K. Johnson of the University of New Mexico has provided the currently available information on habitat use at multiple scales, at numerous nesting colonies in New Mexico. Studies are also ongoing at the Great Basin Bird Observatory in Nevada.