The Double Cone Quarterly
Window to the Wilderness
Summer Solstice 1999 || Volume II, Number 2


Birds of the Ventana Wilderness


Acorn Woodpecker
Melanerpes formicivorus ("Black creeper who devours ants")

by Tom Hopkins

A common and often conspicuous year around resident of the oak woodlands and mixed evergreen forests of the Ventana, the acorn woodpecker is easy to recognize and fun to observe. Mature birds are about 9 inches from the tip of bill to the tip of tail. Their clown-like facial pattern of white, pale yellow and black, with yellow eyes and a red cap, distinguish them from other woodpeckers. Males and females have similar plumage, but the male (shown) has a slightly longer bill and a larger red patch on the head. The red cap on the female is actually separated from the white on the face by a black band that is nonexistent on the male. The backs are black with white wing patches and a white rump patch, which are visible during their undulating flight.

Acorn woodpeckers are the most social of all North American woodpeckers. In most of their range, including the Ventana, they live in communal groups usually comprised of two breeding adults, their immature offspring and occasionally offspring from previous nestings (with other mates). Groups as large as 16 birds have been observed. They are noisy, raucous birds often calling to others in the group: "whack-up, whack-up, whack-up."

During the summer months they feed primarily on insects, often taken on the wing, including grasshoppers, beetles, ants and flies. From autumn through spring they feed on acorns, both green and dried. They hoard large quantities of acorns in communal granaries made by pounding acorns into holes drilled into a variety of trees, utility poles and even wooden buildings. Granaries are used year after year, and can be quite large. Granaries with tens of thousands of acorns have been observed. Their food hoarding habit allows acorn woodpeckers to maintain year around residency, rather than to be forced to seasonally migrate to follow food supplies. They are also known to feed on various cultivated fruits and nuts.

The nests are excavated into snags of a variety of trees and sometimes poles by both sexes of a pair, with occasional help from other adult members of communal groups. The nests, which are typically 12 to 60 feet above ground, have entrance holes 1-3/5 inches in diameter and an inside cavity 8 to 24 inches deep, which is lined with chips from the excavation. Four to six white eggs, about one inch in diameter, are laid from April to June, and second or (rarely) third broods are raised as late as September in years with abundant acorn crops. Both sexes incubate the eggs, which hatch in 11 to 14 days. Young birds fly in 30 to 32 days from hatching. Both parents and other members of communal groups help to feed the young, who become self sufficient in about two months.

References

Ehrlich, Paul R., David S. Dobkin, Darryl Wheye 1988. The Birder's Handbook, a Field Guide to the Natural History of North American Birds. Simon and Schuster, New York.

Peterson, Roger Tory 1990. Western Birds. Houghton Mifflin Co., Boston, Third Edition.

Scott, Shirley L. (ed.) 1987. Field Guide to the Birds of North America. National Geographic Society, Washington, D. C., Second Edition.

Terres, John K. 1996. The Audubon Society Encyclopedia of North American Birds. Random House, New York.

Photographs copyright H. Townner and Loyola Marymount University, all rights reserved.


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