Amongst the birding world, the acorn woodpecker (Melanerpes formicivorus) is rather unique in being highly sociable. This species, common in oak and pine forests of the west, is a commonplace woodpecker species at the UC Hopland Research & Extension Center.
Typically found in highly territorial family groups called "clans" or "colonies", they actually work together to gather food materials, raise young, and defend territories and food reserves. The gathering of acorns and/or pine nuts in the fall and storing them for use throughout the winter is one unique behavior for which the acorn woodpecker is famous.
Here you see acorns stored in the thick bark of a Valley Oak (Quercus lobata) and the photo represents a small portion of this clan's "granary" of stored acorns. At the granary, which is rigorously defended from other woodpeckers and squirrels, the acorns are checked routinely for soundness and sized to fit tightly into an appropriate storage hole. These granaries can be extremely large in size and many are the results of numerous generations of woodpecker work. The larger granaries can hold thousands of acorns, of which the nut "meat" itself is used as a food source for the clan.
