Williamson's Sapsucker

Williamson's Sapsucker is unusual among North American woodpeckers for its extreme sexual dimorphism. The male is largely glossy black with bold white wing and rump patches, a white facial stripe, and a small crimson throat patch. The female looks completely different: finely barred brown and black overall with a plain brown head and a yellow-washed belly.

For decades in the 1800s the two sexes were classified as separate species before ornithologists realized they were mates of the same bird. This dramatic difference in plumage remains one of the more remarkable examples of sexual dimorphism in North American birds.

Key Field Marks

• Male: mostly black body, white face stripes, white wing patch, white rump, small red throat patch, pale yellow belly
• Female: finely barred brown, black, and white overall, plain brown head, yellow-tinged belly
• Both sexes show a black bib on the upper breast

Similar Species

• Male superficially resembles a small black-and-white woodpecker but the white rump and wing patches combined with the red throat are diagnostic.
• Female can be confused with a Northern Flicker but is smaller with a shorter bill and finer barring, and lacks the flicker's spotted underparts.
• Other sapsuckers show red on the crown or a fully red head, not just a small throat patch.

Habitat

This species favors open, mature coniferous forests in mountains, especially stands of ponderosa pine, lodgepole pine, and Douglas-fir, often near aspen groves used for nesting.

Range

Williamson's Sapsucker breeds in mountain ranges of the western United States, southern British Columbia, and northern Mexico, including the Rockies, Cascades, and Sierra Nevada.

Migration

Most populations migrate short to moderate distances downslope or south for winter, moving into lower-elevation pine and oak woodlands in the southwestern United States and Mexico.

Behavior

Unlike most sapsuckers, Williamson's Sapsucker feeds heavily on ants, which it gathers from tree trunks and carries to nestlings in large numbers, supplementing this with sap from wells drilled in conifer bark.

Voice

Calls include a harsh, rolling churr and sharp chirping notes; drumming is an irregular, stuttering series similar to other sapsuckers.

Feeding

Adults maintain sap wells in conifers and glean ants and other insects from bark crevices, feeding nestlings almost exclusively ants during peak breeding season.

Nesting

Pairs excavate a cavity, often in aspen or a dead conifer, and both sexes incubate the 3-7 white eggs and share feeding duties.