If you’ve ever heard an odd bird call that sounds a bit like a squeaky toy, it’s likely an Acorn Woodpecker (Melanerpes formicivorus). These small birds can often be seen flitting among the canopy of oak woodlands, where they live year-round. As their name suggests, their diet consists mainly of acorns, however they sometimes eat other seeds, nuts, fruits, insects, and eggs of other birds. Due to their reliance on acorns, these birds live almost exclusively in oak forests. While their population is stable, their reliance on oak trees makes them vulnerable to habitat loss.
Unlike other woodpeckers, Acorn Woodpeckers do not drill for insects, but rather so that they may have cavities to store their acorns for winter. Acorn Woodpeckers live in colonies, each colony having a “granary tree:” a dead tree or telephone pole that can hold thousands of cavities and acorns. These birds nest in tree hollows, where the incubation of eggs and raising of young is done not only by the parents, but with the help of the whole colony (up to 16 birds!). They are ten inches long, and are identifiable by the red plumage on the tops of their heads, the yellow beneath their chins, and their pale eyes. Unlike other woodpeckers of the Bay Area, Acorn Woodpeckers do not have barring on their wings. Acorn Woodpeckers are also relatively large, and can be identified by the white patches on the underside of their wings while in flight. Males and females are similar in size and appearance, however the red plumage of the males covers from the back of their head down to their forehead, while females have a smaller patch on the back of their head. Their calls are distinctive, either a loud repeating “ja-cob!” or “wake-up!” Also listen for the trilling sound of these woodpeckers drilling their granary trees, which can be heard from half a mile away!
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