This Hairy Woodpecker was seen pecking at the fruiting bodies of Annulohypoxylon sp. (formerly Hypoxylon sp.), which is a primary dead-wood decomposer. Dead wood that hosts this fungus is much easier to excavate and is believed to be intentionally spread by the woodpeckers to soften wood before they dig in.
For more information on the topic, here’s an interesting paper from 2016: https://royalsocietypublishing.org/doi/10.1098/rspb.2016.0106
