Nutty for Acorns

In any given grove of oaks in the California Coast Range, there is undoubtedly a granary of acorns belonging to the local “tribe” of Acorn Woodpeckers.  These striking black and white birds are highly gregarious and almost always found in family groups of up to 12 birds.

A group of three male (?) Acorn woodpeckers bring their acorns to the granary tree for storage.

A group of three Acorn woodpeckers congregate on a tree branch while hunting acorns.

The all red crown indicates this is a male.  The white throat and forehead feathers are tinged with yellow.

The all red crown indicates this is a male attending his granary. The white throat and forehead feathers are tinged with yellow.  White breast feathers are streaked with black.  

Woodpeckers drill holes and fill them with acorns.

Woodpeckers drill holes in dead snags or bark of living trees and fill them with acorns.  Note how one set of holes follows a longitudinal crack in the right branch of this tree.

Granaries are re-used over time, and new holes added each year, which the woodpeckers dutifully fill with their harvest.  There seems to be some disagreement about whether the acorns themselves are consumed or the woodpeckers simply store the acorns to have a ready source of insect food from the weevil larvae infesting the nuts.  It’s probably some of both strategies.

The birds seem to be quite fussy about the particular hole chosen for a particular acorn.  I watched this bird transfer a single acorn from one hole to another until it found just the right one.

The birds seem to be quite fussy about the particular hole chosen for an acorn. I watched this bird transfer a single acorn from one hole to another until it found just the right one.

Even more unusual than their extensive food larder is the Acorn Woodpecker’s love life.  Rather than a single pair of breeding birds producing young, the family group breeds communally.  Typically a group of brothers is mated with a group of sisters, all of whom lay their eggs in one large nest hole.  The young are reared communally and often stay with the family group to act as “helpers” during the next breeding season by procuring acorns and feeding the next generation.

"I'm so pretty...oh, so pretty"...

Individuals recognize and keep track of each other through their nasal calls (“waka-waka-waka”) and wing displays.

This excellent video from the Cornell lab of Ornithology relates some of the biology of this interesting bird.  (Best viewed in full screen)

10 thoughts on “Nutty for Acorns

    • Quite a few species employ helpers at the nest. Some years ago when I was doing some research on Tree Swallows, I found that they also utilize helpers (often non-breeding birds reared the year before). Scrub Jays in Florida (and maybe California) also use this strategy, as well as Groove-billed Anis in Texas. About 3% of bird species exhibit some sort of cooperative breeding strategy, so it’s more common than you might think.

  1. I thought it was pretty cool that the Red-headed Woodpeckers store acorns for the winter, but these woodpeckers take that practice up to a new level. The granary trees are amazing. The birds themselves are really striking too. I checked out the range map in my bird guide and realize I will have to head West if I want to see these woodpeckers

    • You’re right — they are similar species, and in fact, closely related; both are species in the genus Melanerpes, along with the red-bellied woodpecker and about 17 other species. Yes indeed, lots of interesting birds out here in the western U.S.

  2. Pingback: woodpecker haven | Back Yard Biology

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