The cerulean warbler is a light blue bird trimmed with black and white. This warbler lives in mature deciduous forests, often in floodplains. They have declined in number due to the destruction of bottomland forests. The cerulean warbler is 4 to 4.5 inches long, has a wingspan of 7.5 to 8 inches and an average weight of 3.2 ounces. Females are slightly smaller than males.
Males are azure blue on the back and white on the belly.
An identifying mark is a dark blue or black line across the throat. They have dark streaking on the flanks and back. Females are dull grey-blue above with a yellowish wash below. Both sexes have two white wingbars. Juveniles are brownish-gray above, with a pale center crown stripe and entirely white underparts.