The California Thrasher is quite similar to Crissal and Le Conte's Thrashers. It has a paler supercilium, darker cheeks and less rusty undertail coverts than the Crissal. Le Conte's is paler overall and lacks the pale supercilium and dark cheeks. The range of the California does not overlap much with the other species. Other thrashers have spotted underparts and pale eyes.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.