Habitat indicators for cavity-nesters: The polypore Phellinus pini in pine forests

- Drained pine wetlands had a sparse tree-cavity supply and few cavity nesters.
- Fruit-bodies of Phellinus pini explained >50% variation in cavity-nester densities.
- Snags and tree-cavity counts were less useful as indicators.
- Phellinus pini can serve as an indicator and flagship for tree-cavity management.