The Crested Auklet is aptly named for its distinctive crest. Only the Whiskered Auklet shares this feature. In alternate plumage, the Whiskered Auklet has three white plumes on the head and a quite different bill shape. In immature plumages where the crest is lacking, the larger size of the Crested Auklet may be the best disinguishing mark. In immature birds, the all dark plumage and smaller bill distinguish it from Tufted Puffins, Rhinoceros Auklets, and Parakeet Auklets.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.