Pied-billed Grebe has thick, horn-colored bill and brown plumage. Red-necked Grebe is much larger, and has a longer bill that is yellow at the base. Horned Grebe is similar, but has a straighter bill without an uptilt at the tip and a blockier head without a peak at the center of the crown. In basic plumage Horned Grebe has a white face, while in alternate plumage it is separated by the golden eyeline and reddish neck. Birds in transition between basic and alternate plumage are best distinguished by structural features, as the plumage can be quite variable.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.