Although not as colorful as some other warblers, the male Cerulean Warbler is recognizable by its white underparts crossed by a thin black band. This field mark is useful since this bird often forages high in the canopy where the pale blue upperparts are not easily seen. Females, and especially immatures, are very nondescript but have bold white superciliums, mostly white underparts, and wing bars. There is often a hint of bluish color, especially on the crown.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.