The male Great-tailed Grackle is similar to the Common Grackle but is larger with a much longer tail. Great-tailed and Boat-tailed Grackles are very similar but fortunately have mostly different ranges. Great-tailed Grackles have paler eyes and different calls.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.