Sunday, May 27, 2012

An Honorary Squirrel: The Acorn Woodpecker

The acorn woodpecker is a bird of the American southwest that has a very squirrel-like habit of storing acorns. In fact, this medium-sized woodpecker is so compulsive about stashing its nuts that it makes the eastern gray squirrel look like a slacker in comparison!

That's right. Each autumn, a family group of acorn woodpeckers may store as many as 50,000 acorns in a single tree, called a granary tree, with each acorn placed carefully in an individual hole drilled for that nut.

Okay, I know that hole is around here somewhere...

This compulsive nut-storing is even more amazing when you consider that the acorn isn't even this bird's primary food. Their main foods are insects, tree sap, and fruits, with the acorns put aside as a reserve food to help them get through the winter.

Acorn woodpeckers are found in mountainous pine-oak woodland areas in southwestern Texas, New Mexico, Arizona, and California in the United States, and in Mexico and Central America. They nest in cavities in tree trunks or limbs. With their black and white face, with the red cap and white eyes, these colorful woodpeckers have been described as clown-faced.

Acorn woodpeckers live in large and complex extended family groups that usually contain more than a dozen individuals. Families hold and defend territories. After young are raised, they may stay with the parents for several years to help their parents raise subsequent young.

The most important food is insects, which the birds glean from tree branches or catch from perches at the top of the tree canopy. However, a large amount of the acorn woodpecker family's time is devoted to creating and maintaining their huge acorn granaries. The granary may be in any tree, living or dead. In suburban areas, acorn woodpeckers may use a utility pole or even the wooden siding on a building, which can't make homeowners very happy!

An acorn woodpecker granary

The acorn woodpecker is unique in the level of cooperation that family groups devote to this communal food hoarding. The family will defend its granary against all acorn thieves, including woodpeckers and other birds such as jays, and, yes, squirrels.

Who are you calling a thief?

If you would like to read more about the acorn woodpecker, this article from the Cornell Lab of Ornithology has more information about its family structure and food hoarding habits.

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