Mystery Bird: Acorn Woodpecker, Melanerpes formicivorus

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[Mystery bird] Acorn Woodpecker, Melanerpes formicivorus, photographed in China Camp State Park, Point San Pedro Peninsula, California. [I will identify this bird for you in 48 hours]

Image: Joseph Kennedy, 11 May 2010 [larger view].

Nikon D200, Kowa 883 telescope TSN-PZ camera eyepiece 1/400s f/8.0 at 1000.0mm iso400.

Please name at least one field mark that supports your identification.

This bird has a very unusual behavior that is a response to the availability of its primary food supply. Can you tell me what this bird usually eats and what this unusual behavior is?

I purposely kept this question vague because I was interested in what you all would dig up, especially since this species' "food politics" and behavior are really quite fascinating. First of all, this species is an omnivore, consuming all sorts of things from leaf buds to insects and their larvae, and even small lizards. But their main food, particularly in the winter, is acorns. To that end, they form groups that collect acorns that they dry and store in large granaries. These granaries are constructed by the birds, which bore acorn-sized and -shaped holes into dead trees and other wood items that serve to store individual acorns.

The unusual behavior that I was intending to tell you about is this: acorns are such an important resource to the California populations of Acorn Woodpeckers that they may nest in the fall -- a rare behavior in birds -- to take advantage of a large fall acorn crop [Koenig, W.D., and Stahl, J.T. (2007) Condor; 109(2):334-350]

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No mystery here. This is an acorn woodpecker. Definitive field mark is the unique 'clown face' with large black white and red patches. It's main food is, well, really, acorns. It stores them in granaries built over generations of woodpeckers. It breeds in groups. A friend of mine, Walt Koenig (we were graduate students together at UC Berkeley) has studied them his entire professional career (he's now at Cornell). He and Ron Mumme, another fellow student, published years ago that if a female begins laying eggs in the colony before other females are ready, they will take the early egg to an acorn storage tree and eat it, in a group. Ron, always one for clarity, named this "communal egg sucking in acorn woodpeckers."

These little rascals use the siding on our house as one of their granaries! We have a 15 minute standoff/stare down every morning around 9:45 as the group makes it morning rounds through the forest. We are helpless in the face of their persistence.

By ears akimbo (not verified) on 06 Jul 2010 #permalink