In breeding plumage, the brown and white plumage of the Marbled Murrelet is similar only to the Kittlitz's Murrelet. However, the Kittlitz's has a white belly and white outer tail feathers. In winter, the white scapulars dividing the dark back and wings are diagnostic and can only also be found in the Kittlitz's murrelet. However, it has a dark cap that does not include the eye and a more complete breast band. Juvenile Marbled Murrelets might be confused with juvenile Pigeon Guillemots but are smaller, have shorter necks, bills, and no white in the wing. An asian species, the Long-billed Murrelet, formerly a subspecies, is a casual stray to the United States (especially inland) and differs in its larger bill and face pattern.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.