Adult males are iridescent black on their head, back, sides and tail. They have a white stripe behind the eye and a lower white stripe across each side of the head, a red chin and a bright yellow belly. They have black wings with large white patches. The female is completely different in appearance: mainly black, with a pale yellow breast, a brownish head with black streaking and fine barring on the back, breast and sides. Originally, the female was considered to be a different species and named the
black-breasted woodpecker by Cassin.
Measurements: •
Length: 8.3–9.8 in (21–25 cm) •
Weight: 1.6–1.9 oz (44–55 g) The species took its common name from Lieutenant
Robert Stockton Williamson, who was the leader of a
surveying expedition which collected the first male. They were trying to identify the best route west for a railway to the
Pacific Ocean. == Subspecies ==