Male Rusty Blackbird similar to male Brewer's Blackbird but lacks purple iridescence. Female Rusty Blackbird has a light eye. Grackles are larger with much longer tails. Cowbirds are smaller with more conical bills.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.