Williamson's sapsucker, Sphyrapicus thyroideus, occurs in western North America, where it ranges from southern British Columbia to central Mexico. It is found in Utah mainly in the mountainous areas of the eastern two-thirds of the state, where it is an uncommon breeder. On its breeding grounds, the habitats used by this species are middle - to high - elevation coniferous forests and mixed deciduous-coniferous forests containing aspens. The foods of this species include insects, especially ants, and the sap of conifers and aspens.
This woodpecker excavates a cavity in a tree, typically an aspen or a conifer, usually three to sixty feet above the ground, this process taking three to four weeks. Three to seven (usually five or six) eggs are laid. The eggs are incubated, by both parents, for twelve to fourteen days before hatching. Both parents care for the nestlings, which fledge in three to four weeks.
The common name of this woodpecker honors Robert Stockton Williamson, a lieutenant in the United States Army in charge of the Pacific Railroad Survey in California and Oregon, under whose command some specimens of this bird were collected in 1857.