The adult male Canada Warbler is instantly recognizable with its black necklace. Females and immatures also have the diagnostic necklace but it is gray and less noticeable. The combination of gray upperparts, no wing bars and yellow underparts is unique.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.