10 Unique Facts About Acorn Woodpeckers

Acorn woodpeckers live in western Oregon and California, Washington, Colorado, New Mexico, and western parts of Texas. 

They are often found in oak woodlands but can be spotted in other types of forests, as long as oaks are nearby. More commonly, they are found in mountainous areas but will visit lowland valleys.

These clownish-faced birds have an incredibly unique social structure. This involves cooperative breeding, mate sharing, helper birds, and team efforts.

They prolifically store acorns and will defend their territory with parrot-like calls.

Read on to learn all about this unique species of woodpecker.

1. Acorn Woodpeckers Have A Clownish Face

The acorn woodpecker is often described as having a “clown face”. 

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Males have a red crown extending from the top of the eyes to the nape. Females have less red on their crowns, with it restricted to just the back of their heads. 

The forehead, base of the bill, chin, and upper throat are glossy black and bordered with a white band. They have a black mask that goes around the eyes and connects to the black body.

Their underbellies are white or creamy, with streaks of black. When they fly, 3 black and white flashes are visible on each wing, along with a white rump.

Their wild-looking white eyes add to their clownish look.

Juvenile acorn woodpeckers are duller in color overall, with darker-colored eyes. Their underbelly feathers may appear tan in color rather than white. 

There are 7 subspecies of the acorn woodpecker with some slight variances in their overall plumage colors and patterns.

2. They Have An Unusual Social Family Structure

Acorn woodpeckers are the focus of long-standing research studies to observe the birds’ unusual social behavior. 

This involves dynamics such as mate-sharing, infanticide, and other group dynamics. (More on that below.)

Unlike other woodpeckers, these birds live in family groups of 12 or more members. They work together to raise families, guard territories, and store food. 

Young woodpeckers will stay with the group for several years to help with the colony.

3. Acorn Woodpeckers Hoard, Check & Guard Acorns

Hoard Acorns

Acorn woodpeckers are given their name for their large hoarding practices in storing acorns. They harvest acorns in the fall and drill small holes in dead trees to store them. 

The acorns are reserved for the winter season when food is in short supply. By having an ample food supply, this woodpecker does not need to migrate to look for other sources of food in the winter.

Trees may have up to 50,000 holes in them and are referred to as “granary” trees. Generations of acorn woodpeckers will reuse a granary tree, reusing previously drilled holes as well as forming new ones.

Holes are often started a few feet up the trunk from the ground to naturally keep ground pests from accessing the acorns. They also use naturally formed holes and cracks in tree bark to store acorns without the need for drilling.

Acorn woodpeckers primarily store acorns from oak trees. However, they will also store almonds, walnuts, pecans, hazelnuts, and pinyon pine nuts. 

Check Acorns

Since the acorns will shrink as they dry out, the woodpeckers test the acorns to make sure they are snug in the holes. 

They turn them to wedge them in or tap the acorns to make sure they are in tight. They may also move them to a smaller hole for a better fit.

Guard Acorns

Members of the group guard the tree, and up to 15 acres of territory surrounding it. 

These guard birds will protect the stash from thieves, sounding an alert if a threat is nearby. Several other members will race through the trees with parrot-like calls to scare off the intruder.

4. They Store Acorns In Wooden Man-Made Structures

Acorn woodpeckers can be a problem for homeowners with wooden structures and wooden siding. These birds will use wooden man-made structures as acorn granaries. 

To repel these woodpeckers, people often try scare tactics such as hanging shiny reflective tape from their wooden-sided sheds and homes. 

However, in many cases, they have to replace the siding with a non-wooden material to fully keep them away.

Acorn woodpeckers also store nuts in fence posts, utility poles, and porches.

5. A Group Of Acorn Woodpeckers Is Called A Bushel

A family of acorn woodpeckers is called a “bushel”. This word represents a volume of dry goods. 

This seems an appropriate word for their cooperative way of storing large amounts of acorns in granaries. Acorn caching is a large part of the acorn woodpecker’s daily activities.

6. Acorn Woodpeckers Eat More Than Just Acorns

Acorn woodpeckers have an omnivorous diet, eating more than acorns and other kinds of nuts. They may visit seed and suet bird feeders, eat fruits, and drink sap and nectar.

They rarely drill into the wood for insects like other woodpeckers, but rather catch them on the wing or glean them from surfaces. They hunt ants, beetles, and other insects, and will cache these in cracks and crevices as well.

These birds also eat lizards and eggs, including eggs of their own species.

7. They Sound Like Parrots

Acorn woodpeckers produce parrot-like calls that sound like “waka-waka”, “ja-cob, ja-cob”, or “wake-up, wake-up”. 

They also produce a typical woodpecker drumming sound when they drill holes in wooden surfaces.

Here’s a recording of an acorn woodpecker’s call:

8. Acorn Woodpeckers Share Mates

Each family group of acorn woodpeckers breeds in a polygamous way. This includes up to 8 breeding males and 3 breeding females in each group. 

The males share mates with their brothers, creating breeding practices within sibling groups.

Any members of the colony that do not get to breed will look for vacancies in other groups up to 10 miles away.

9. Breeding Female Acorn Woodpeckers Share A Single Nest

Breeding females lay their eggs in the same nest cavity. Interestingly, if there are any eggs in the cavity before she lays (from another female), she will destroy them. 

More than one-third of eggs laid in a shared nest are destroyed. These egg pieces are moved to a nearby tree where the colony eats them, including the female that laid them.

Once all breeding females in the group are laying eggs, they stop destroying them. This may be so that all eggs hatch at approximately the same time. 

Generally, there are 3 to 7 white eggs (or more) in a nest once egg-laying is synchronized. Often, the last female in the colony to produce eggs ends up having more of her own incubated.

10. Helpers Assist With Nesting, Incubation, & Feeding

Cooperative breeding is rare, found in only about 9% of bird species. Acorn woodpecker colonies will raise 1 to 3 broods each year. 

Members of the family group work together to raise the offspring. Adults and helpers (other young, maturing offspring born a previous year) excavate a nest cavity. 

However, a nest cavity is often reused from a previous year. (They also excavate other holes for acorn storage and roosting together.) 

Cavities are about 6 inches in diameter, and 8 inches to 2 feet deep. They are lined with a fresh layer of wood chips. They will peck at the cavity walls to make fresh layers of wood chips as needed.

They then take turns incubating the eggs for 11 to 14 days and then feed the hatchlings. The fledglings are ready to leave the nest in 30 to 32 days. 

These young chicks remain with their family for several years, becoming helpers to raise successive broods. Eventually, these helpers will leave for other territories to fill breeding vacancies.

Conclusion 

The acorn woodpecker uses trees and man-made wooden structures for storing thousands of acorns each year. 

They work in cooperative family groups, called bushels, to share mates, build cavities, incubate eggs, and raise the young. 

Interestingly, breeding females in the family share one nest. When they go to lay eggs, they often destroy and eat other eggs already in there until all females are actively laying eggs. 

The colony works together to raise the young and secure their acorn cache for the winter season.

These facts and more make the acorn woodpecker quite different from other woodpecker species.

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