The Western Bluebird (Sialia mexicana) is a small Thrush, about 15 to 18 cm (5.9 to 7.1 in) in length. Adult males are bright blue on top and on the throat with an orange breast and sides, a brownish patch on back, and a gray belly and undertail coverts. Adult females have a duller blue body, wings, and tail than the male, a gray throat, a dull orange breast, and a gray belly and undertail coverts. Immature birds have duller colors than the adults, and have spots on their chest and back.