Acorn woodpeckers (Melanerpes formicivorus), which I introduced yesterday, eat insects, tree sap and fruits. They can often be seen catching insects high above the tree canopy or gleaning them off the limbs of trees. The species name for the acorn woodpecker, formicivorus, actually refers to the ants (“formic”) that they eat.
Ants, however, are not the primary food of acorn woodpeckers. Acorns (surprise!) comprise the main portion of their diet. Extended family groups live in oak woodlands and stash acorns in a dead tree, or even a telephone pole. The acorn woodpeckers drill holes in the tree and push acorns into these cavities. The fit is very tight and often even the woodpeckers cannot retrieve their hoard. Over the years these storage trees, called granary trees, can hold thousands of acorns. In the winter, when food supplies are short, the granary tree provides sustenance for the acorn woodpeckers who maintain the tree. Drilling holes in the tree, collecting and stashing acorns and defending the granary occupy a large portion of the family’s time and energy.
The group that I was watching along the Pacific Crest Trail (Shasta County CA) had a dead ponderosa pine (Pinus ponderosa) amid California black oaks (Quercus kelloggii) as their granary tree. One photograph shows the cached acorns and in another a woodpecker is drilling a hole in the granary. This granary tree is about thirty feet high. An acorn woodpecker can be seen at the top of the tree in the third picture.
Tomorrow – the unusual social structure of an acorn woodpecker family group.