Acorn Woodpecker Melanerpes formicivorus
March 12th 2011 20:52
Illustration by Donald L. Malick
This conspicuous clown-faced woodpecker of western oak woodlands is remarkable for its social habits, living over much of its range in communal groups of up to 4 or more breeding males and as many as 3 breeding females. These groups maintain and protect impressive granaries in which thousands of acorns are stored in holes drilled in tree trunks or utility poles for future consumption; in a study a single tree contained more than 50,000 acorn-storage holes. Acorn woodpeckers also feed by sallying for flying insects and gleaning trunks, and they often eat ants (as reflected in the species’ scientific name). Polytypic. Length 9" (23 cm).
Identification A boldly patterned black-and-white woodpecker with a white patch at the base of the primaries, a white rump, black chest, streaked black lower breast, and white belly. The head pattern is striking, with a ring of black around the base of the bill, a red crown patch, a white forecrown narrowly connected to the yellow-tinged white throat, and black sides of the head setting off a staring white eye. Adult: iris white. Adult male has white forehead meeting the red crown. The adult female is similar, but the white forehead is separated from the red crown by a black band. Juvenile: resembles adult but black areas are duller and the iris is dark; juveniles of both sexes have a solid red crown like that of the adult male.
Geographic Variation Pacific coast birds, bairdi, have slightly longer and stouter bills than nominate birds of the interior West. There is considerable additional variation in the remaining range south to Colombia, with 5 additional subspecies.
Similar Species Unmistakable given its group-living habits and loud calls. White-headed woodpecker has similar white wing patch and black back, but lacks white rump and belly; Lewis’s lacks white areas in plumage.
Voice The acorn is noisy and conspicuous in communal groups, with raucous “Woody Woodpecker” calls. Call: loud wack-a, wack-a or ja-cob, ja-cob series. Also, a scratchy, drawn-out krrrrit or krrrit-kut, and a high, cawing urrrk. Drum: a simple, slow roll of about 10–20 beats.
Status and Distribution Common. Year-round: oak woodlands and mixed oak-conifer or oak-riparian woodlands. Most abundant where several species of oaks co-occur. Isolated breeding populations are found on the east side of the Sierra Nevada, California; on the central Edwards Plateau, Texas; and possibly in far southern Colorado. Vagrant: found rarely or casually, primarily in fall and winter, away from woodland habitats along the immediate Pacific coast and in western deserts; accidental north to British Columbia and east to the Great Plains states from North Dakota south to coastal Texas.
Population Stable, apart from some local declines resulting from degradation of oak woodlands.
—From the National Geographic book Complete Birds of North America, 2006
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