Most species of woodpeckers drill into dead trees, referred to as "snags," and excavate a cavity in them for nesting. Only one species, the Red-cockaded Woodpecker, actually uses living trees as a nesting site. Also unique among woodpeckers, this species lives in colonies. Mature pines are the tree of choice, particularly ones with red-heart fungus. A fungus-infected tree is easier to excavate because the center of the tree is dead. The living tree is harder to peck through, but the living tree is important in the life history of the bird. Red-cockaded Woodpeckers flick layers of bark off the tree above and below the nest hole.