Breeding males are glossy black with purplish head and greenish sheen on body. Nonbreeding males have pale eyebrows and staring yellow eye. Females are plain dark brown and typically have dark eyes. Forages by walking on ground.

​This species was discovered by John James Audubon on his final expedition in 1843 and named for his friend Dr. Thomas Brewer, a Boston ornithologist, who probably never saw a live Brewer’s Blackbird.