Woodpeckers belong to the family Picidae. Most species excavate wood to find insects and larvae, often supplementing this diet with tree sap. This foraging behavior allows them to access protein-rich food hidden beneath the bark. However, a select few species have evolved a highly specialized method of food acquisition and storage centered on a different resource entirely. Yes, some woodpeckers eat acorns, driven by a unique adaptation for long-term food security rather than simple foraging.
The Acorn Specialist
The species responsible for this unique behavior is the Acorn Woodpecker. Unlike many relatives, this bird has developed a dependence on the acorn crop for survival. They are easily recognizable by their bold, “clown-faced” pattern of black, white, and red, and their striking white eyes. While other woodpeckers are solitary, the Acorn Woodpecker is highly social, living and breeding communally in family groups of up to 16 individuals. This cooperative social structure supports their specialized feeding habit, as managing the food supply is a group effort. Acorns can make up about half of their annual diet, becoming the major food source during the non-breeding season.
The Granary System
The Acorn Woodpecker creates and maintains a communal food store known as a granary. These granaries are dead trees, utility poles, or wooden buildings riddled with thousands of small, individually drilled holes. The woodpeckers meticulously hammer acorns into these custom-sized cavities, wedging them tightly so that other animals cannot pry them out. A single granary may be used for generations, accumulating up to 50,000 holes filled with nuts. This system protects the harvest and allows the acorns to dry out, requiring the woodpeckers to constantly move the shrinking nuts to smaller, better-fitting holes to ensure a dependable, year-round food supply defended by the entire group.
Why Acorns and Not Just Insects?
Reliance on acorns is a strategy for surviving periods of scarcity, particularly the winter months when insects are less available. While insects offer high-quality protein, acorns provide large amounts of carbohydrates and fats, serving as a storable, energy-dense resource. This ability to stockpile food allows the Acorn Woodpecker to remain a permanent resident in its habitat, unlike many insect-eating birds that must migrate south. The stored acorns are important for the adult birds, whose diet can consist of up to 90% acorns in some seasons, while they feed the young protein-rich insects. This dual-diet approach allows the adults to sustain themselves. The stable, long-term resource provided by the granary underpins the species’ complex social life and its ability to thrive in oak woodlands.