Monday, January 17, 2011

Blue Jay

The blue jay is a familiar and widespread bird throughout the East. Generally loved or hated, it has acquired a Jekyll-and-Hyde reputation. It is a frequent visitor to backyard feeding stations, where its raucous and rambunctious behavior is well known, but this adaptable jay is equally at home stealthily moving through the forest, plundering other birds’ nests, searching for nuts, or quietly raising its young. Polytypic. Length 11" (28 cm).

Identification The blue is a nearly unmistakable crested jay with black barring and white patches on blue wings and tail; its underparts are paler with a dark necklace. Juveniles are more grayish above with gray lores and more limited white markings on the wings.
Geographic Variation Minor, obscured by broad overlap. Three subspecies are generally recognized. Northern bromia average the largest and brightest. Southeastern cristata generally show a subtle violaceous wash and are smallest. Western cyanotephra are generally duller and paler blue.
Similar Species Nearly unmistakable. Occasionally hybridizes with the Steller’s jay; hybrids appear intermediate between the 2 parent species.
Voice Vocal with a diverse array of vocalizations. Call: a piercing jay jay jay; a musical yo-ghurt; frequently imitates raptors, particularly the red-shouldered hawk. Actively migrating birds are typically silent.

Status and Distribution Common. Breeding: a variety of mixed forests, woodlands, suburbs, and parks. Migration: diurnal migrant. Northern populations move south in varying numbers from year to year. During flight years, large loose flocks can fill the sky, particularly along the shores of the Great Lakes and other northern locations known for raptor concentrations. In fall, first detected away from breeding grounds as early as July (typically earliest in big flight years); peaks in Great Lakes late September–mid-October. Winter: distribution generally similar, but departs from northernmost breeding locales. Vagrant: casual chiefly in fall and winter west of the Rockies, recorded most frequently in the Northwest. Accidental to Bermuda.

Population Numbers are increasing in parts of the West. Domestic cats are likely the most significant human-caused source of mortality.
—From the National Geographic book Complete Birds of North America, 2006