In the non-breeding season, it winters on the eastern slope of the Andes in South America, preferring subtropical forests.

Females and immature birds have bluish-green upperparts, a pale stripe over the eye, no streaking, and are yellow below.

[11] The change was implemented as part of the Fifty-second Supplement to the AOU Checklist of North American Birds.

Older individuals have stronger colors across the entire body, including brighter whites, darker streaking, and wider breast bands.

[22] The beak and legs of the cerulean warbler vary in color depending on an individual's age and sex.

Adult males have a black beak, with the lower half a slightly lighter dark grey.

[24] The cerulean warbler's preferred summer habitat consists of large, unfragmented mature deciduous hardwood forests.

[25] Nesting takes place in the top canopy, often above heights of 30 m (98 ft), and territories are typically about 2 ha (4.9 acres).

Generally, to support a population of cerulean warblers, a forested area of greater than 700 ha (1,700 acres) is required.

Historically, the cerulean warbler was common to abundant as far south as Alabama and Mississippi, but loss of habitat in these southern regions has caused the centre of its breeding range to shift northwards.

In the spring, it takes an overland route through Central America, passing over water only to cross the Gulf of Mexico at the Yucatán Peninsula.

In the autumn, it may overfly the Caribbean Sea, crossing from Florida to Cuba onto continental South America.

[30] The non-breeding range covers a broad area of northern South America, and extends southwards along the Andes mountains.

Its preferred prey consists of butterfly and moth (lepidopteran larvae), though it supplements its diet with winged insects.

[37] At the high elevations and relatively sparser vegetation that the cerulean warbler prefers, the gleaning technique it uses is more effective than aerial maneuvring.

The nest itself is made from tree bark, grasses, and lichens, woven together using caterpillar silk and spider thread.

Young individuals have somewhat different feeding patterns than adults, preferring riparian areas with relatively little foliage.

However, its eggs and young still fall victim to predators such as raccoons, squirrels, chipmunks, snakes, and even other birds, in particular blue jays (Cyanocitta cristata).

[52] Nest parasitism by brown-headed cowbirds (Molothrus ater) occurs, but is less common in the dense interior canopy the cerulean warbler prefers.

Cerulean warblers depend on shade coffee plantations for the mature forest habitat they require.

[54] In fragmented forest areas, the cerulean warbler is vulnerable to nest parasitism by the brown-headed cowbird.

Historically, the preferred habitat of tall forest interiors protected it from brood parasitism, but deforestation has caused the cerulean warbler to often choose nest locations accessible to cowbirds.

[55] This bird's numbers are declining faster than any other warbler species in the USA; its population in 2006 was less than one-fifth of what it was 40 years before.

[56] The American Bird Conservancy (ABC) is working with its Colombian partner, Fundación ProAves, to protect wintering habitat for cerulean warblers and other migratory songbirds.

[60] In San Vicente, Colombia, the cerulean warbler is commemorated in an annual migratory bird festival.

[61] The Man in the Yellow Hat publishes a book about the cerulean warbler in the episode "The Big Picture" of Curious George.