Distribution: The American three-toed woodpecker, Picoides dorsalis, occurs in North America from Canada south to New Mexico and Utah in the west and from Canada south to Minnesota and New York in the east.
The American three-toed woodpecker is found in Engelmann spruce, sub-alpine fir, Douglas fir, grand fir, ponderosa pine, tamarack, aspen, and lodgepole pine forests (Gabrielson and Jewett 1940, Farner 1952, Larrison and Sonnenberg 1968, Marshall 1969). In Utah, this woodpecker nests and winters in coniferous forests, generally above 2400 m (8,000 ft) elevation (UDWR 1998). American three-toed woodpeckers stay on their territories year-round, though insect outbreaks, such as spruce bark beetle infestations, may cause irregular movements (Yunick 1985, USDA 1975, Sphar et al. 1991).
Ecology: American three-toed woodpeckers breed in May, June, and July. The male attracts the female by drumming, then performs a head swaying and calling display (Ehrlich et al. 1988). Both sexes excavate a new nest cavity each year 0.9 - 15 m (3-50 ft) (usually 1.5 m - 3.7 m [5-12 ft]) high in a dead or live tree where they incubate an average of four eggs for 11-14 days (Ehrlich et al. 1988; Spahr et al. 1991; Stokes 1996; DeGraaf et al. 1991). Young fledge at 22-26 days and remain with the parents for another month (Spahr et al. 1991).
Where food is abundant they may nest in loose colonies (Ehrlich et al. 1988; Stokes 1996). Tree species used for nesting are spruce, tamarack, pine, cedar, and aspen trees, but lodgepole pine, balsam fir, and poles are also used (Goggans et al. 1988; Ehrlich et al. 1988; DeGraaf 1991). A pair bond is maintained all year and in successive years, and they exhibit strong breeding site tenacity (Ehrlich et al. 1988). The male roosts nightly in the nest throughout incubation; both adults brood the young. Family cohesion lasts well into the summer months after the young have fledged (ibid.).
American three-toed woodpeckers forage on scaly-barked trees such as spruce, hemlock, lodgepole pine, and tamarack (Stokes 1996; Spahr 1991; Beal 1911). In burned areas they have been documented foraging on moderately burnt spruces in and immediately under the bark, predominantly on bark beetle larvae (Murphy and Lehnhausen 1998). Greater than 75% of their diet consists of wood-boring insects, mostly beetle larvae (61%), but they also eat wood-boring lepidoptera (mainly moth) larvae (14%), and occasionally fruit and sap at sapsucker pits (Spahr et al. 1991; Ehrlich et al. 1988). Spruce beetles comprise approximately 65% of their annual diet, and 99% of their winter diet (DeGraaf 1991).
Habitat Requirements: American three-toed woodpeckers depend on live and dead trees for both nesting and foraging. They require soft wood for excavation because of morphological adaptations associated with three toes on each foot, therefore presence of heartrot is important. Trees with scaly bark remaining on the tree are important to support their foraging technique. American three-toed woodpeckers require trees infested with bark- and wood-boring insects for foraging. American three-toed woodpeckers may require occasional forest insect epidemics (USDA 1975; Goggans et al. 1988).
Use of snags after stand replacing fires is also important for American three-toed woodpecker foraging. Murphy and Lehnhausen (1988) found that three-toed woodpeckers foraged heavily on moderately charred spruce trees the first three years after a fire, and population densities increased. After three years, densities declined to previous levels.