The Acorn Woodpecker

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Woodpecker Habits

Food sources

Reasons they attack

Woodpecker Types

Acorn

Description

The Acorn Woodpecker (Melanerpes formicivorus) is a small to medium sized woodpecker, averaging about 9 inches (23 cm) in length. The adults have black heads, back wings and tails, white chest and facial markings and large white eyes. The adult male has a red cap starting at the forehead; females have a black area or stripe between the forehead and the cap. The combination of the white eyes and facial markings against a black background make this species particularly striking, and a little crazy looking.

Territory

The Acorn woodpecker is a bird that likes a moderate climate and a stocked pantry. They are found from Southern Oregon in the western United States south to Columbia, keeping to elevations that support oak and mixed pine forests.

Behavior

This type of woodpecker is a notorious food-hoarder and is known for drilling closely spaced holes just large enough to accommodate one acorn each. This behavior seems to be somewhat determined by where in the range they live.

Hoarding behaviors are far more common in the north, through California and Oregon. In the southwestern branches through to the tropics, Acorn woodpeckers are far less likely to build granaries, more often using naturally occurring storehouses if they hoard at all. Once the stores are eaten, the woodpecker will move on to a location where food is readily available, typically south in the range.

Acorn woodpeckers are generally a non-migrating breed and need wooded areas with mature oaks, enough to produce adequate quantities of acorns. They prefer to nest in cottonwoods, oaks or ponderosa pine on the underside of large limbs and will reuse the same nest year after year. When these birds cause damage to property, it is usually related to food gathering and storage.

Acorn Woodpeckers will attempt to store food in fences and utility poles, the sides of wooden buildings, and in any number of other undesirable locations, even after it becomes clear that they can’t get them out again. In Arizona, woodpeckers put over 450 pounds of acorns into a water tank, but they will also drop them down stove and rain pipes.

Quick facts

Aside from its exceptionally well-developed food-hoarding practices, the Acorn Woodpecker has a most unusual breeding system as well. Acorn woodpeckers live in family groups that can include multiple breeding females and multiple breeding males. In addition to the breeding members of the group, there are often several non-breeding helpers. Family groups can be quite large, up to 15 members, all of whom participate in young-rearing, territory and granary defense.
When groups have multiple breeding females, all of the females lay their eggs into a single nest that will then be guarded and incubated by the breeding males in the group. Unfortunately, a female will usually clear the nest of eggs prior to laying and as a result about 30%-40% of Acorn Woodpecker eggs are destroyed by other females in the group. Once all females in the group begin to lay, they stop clearing the nest and the remaining eggs are cared for by the group.
Acorn woodpeckers were considered a food source by native peoples of North America. In general, woodpeckers aren’t considered “good eats” because they have an unusual smell, dead or alive. Early naturalists thought this was a result of their insect diet, and since Acorn woodpeckers eat more plant materials than many of their cousins, it might have made them a little more palatable.
All members of an Acorn Woodpecker family group spend large amounts of time storing food, frequently acorns. Acorns typically are stored in holes drilled into a single tree, called a granary tree. One granary tree may have up to 50,000 holes in it, each of which is filled with an acorn in autumn. In addition to the primary granary tree, families may have one to six secondary granaries.
Each acorn-sized hole takes a woodpecker about an hour to drill. A family group of five Acorn woodpeckers will create about 480 holes per year, mostly in winter. Because of this investment in time and energy, Acorn woodpeckers are highly territorial and protective of their granaries, usually against squirrels, jays or other woodpeckers. The whole family group participates in the defense of the granary.

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