title: Double keystone bird in a keystone species complex.
abstract: Species in a Colorado subalpine ecosystem show subtle interdependences. Red-naped sapsuckers play two distinct keystone roles. They excavate nest cavities in fungus-infected aspens that are required as nest sites by two species of swallows, and they drill sap wells into willows that provide abundant nourishment for themselves, hummingbirds, orange-crowned warblers, chipmunks, and an array of other sap robbers. The swallows thus depend on, and the sap robbers benefit from, a keystone species complex comprised of sapsuckers, willows, aspens, and a heartwood fungus. Disappearance of any element of the complex could cause an unanticipated unraveling of the community.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
authors.forename: G C
authors.initials: GC
authors.lastname: Daily
authors.forename: P R
authors.initials: PR
authors.lastname: Ehrlich
authors.forename: N M
authors.initials: NM
authors.lastname: Haddad