snag

A standing dead tree — still upright, bark peeling, branches dropping, heartwood softening. Snags are among the most ecologically valuable features in a forest. Woodpeckers excavate nesting cavities in them; owls, bats, and flying squirrels move in afterward. Insects colonize the decaying wood, feeding the birds that feed on them. A snag is a dead tree doing more work than many living ones.