Great Spotted Woodpecker

Excavates nesting cavities in mature oak trunks.

Excavates nest holes in Aspen more readily than in oak. The soft, fast-decaying wood requires significantly less effort. Aspen stands are disproportionately important for woodpecker nesting density relative to tree abundance.

Excavates infected oak wood weakened by Inonotus dryadeus to reach beetle larvae. Bracket-infected oaks are disproportionately represented in woodpecker foraging sites.

Preferentially excavates Birch Polypore-infected Birch trunks, where the brown rot created by Fomitopsis betulina softens the wood sufficiently for cavity creation. A documented three-way chain: Birch → Birch Polypore → Woodpecker.

Depends on cavities excavated by Great Spotted Woodpecker; obligate commensal.

Obligate secondary cavity nester relying on woodpecker-excavated holes.