- Mary K. Hanson
- Posted On
Tuleyome Tales: Acorn woodpeckers aren’t just the clowns of the forest
NORTHERN CALIFORNIA – Acorn woodpeckers are often referred to as “the clowns of the forest” for their raucous calls, bright faces and tree-top antics, but they’re actually quite complex little birds that dictate how some aspects of the environment grows up around them.
You’ve no doubt seen these guys. Their black, white and red coloring, and bright yellow-white eyes make them unmistakable.
The males and females are patterned similarly, but you can tell the difference by looking at the head. On the males, the red cap starts right after the white forehead; on the female, the red cap is pushed back a little bit and there’s a black band between the white forehead and the red cap.
These birds form social groups that are something akin to blended families consisting of a minimum of three males and two females that all breed cooperatively.
Although females will sometimes pillage other female’s eggs early on in the breeding season, once all of the females in a group start laying, the pillaging stops, and they all share the same nest and take part in the incubation duties.
Acorn woodpeckers nest in cavities in trees that they drill out for themselves and often reuse from season to season.
Inside the cavity, the wood shavings left over from the drilling process act as the woodpecker’s only form of nesting material; the birds don’t gather grasses or twigs for their nests. If the nest is an old one, the woodpeckers will scrape the walls inside of the cavity to build up more, fresher wood chips for the babies.
Young acorn woodpeckers are waited on by all of the adults in the group, both males and females, until they fledge. Fledglings will often stay with their family group for several years before heading off to form new groups or joining an existing group that is short of members.
Groups of acorn woodpeckers are highly territorial, often commanding about 15 acres of the landscape around their nesting and “granaries” –dead tree limbs perforated with thousands of holes.
The woodpeckers drill holes of varying sizes into the wood and then fill them with acorns, other nuts and sometimes even insects. I saw one acorn woodpecker cram the chrysalis of a pipevine swallowtail butterfly into one of the holes of his granary tree.
The birds usually only drill new holes in the trees in the winter, and they only drill in limbs that are already dead or dying, so they do no harm to the living parts of the tree.
If useful trees aren’t available, these woodpeckers will use whatever is locally available to them including wooden fence posts and derelict vehicles.
There was a report from Arizona that documented a large family of acorn woodpeckers filling up a wooden water tank with acorns over a period of several years until the contents weighed almost 500 pounds!
The granary trees and their food caches – which are staunchly protected by the family group from interlopers like starlings, scrub jays, and squirrels – sustain the woodpeckers during the winter when their favorite food, flying insects, is in short supply.
Acorn woodpeckers also like to eat sap, the catkins and pollen from oak trees, and even lizards on occasion.
It’s their granaries that makes acorn woodpeckers a “focal species” as described by the U.S. Forest Service. Focal species are those that are “chosen for special attention ... to be used to guide components of conservation planning such as selection and design of habitat reserves, habitat restoration and management, and population monitoring.”
These woodpeckers are also considered a “keystone species” in the oak woodlands they inhabit because other crevice-nesting birds like tree swallows and house wrens who can’t excavate their own nesting holes depend on the woodpeckers to do that for them.
So, you see: Acorn woodpeckers aren’t just the “clowns” of the forest, they’re also the social and focal species of the forest that helps to define their environment.
Tuleyome is a501(c)(3) nonprofit conservation organization based in Woodland, Calif. For more information, visit www.tuleyome.org . Mary K. Hanson is a Certified California Naturalist and author of the “Cool Stuff Along the American River” series of nature guides available at www.lulu.com .