Cerulean Warbler (CERW)

Setaphaga cerulea

Male Cerulean Warbler © Pam Linge / Macaulay Library
Female Cerulean Warbler © John King / Macaulay Library

Range

This warbler is a long-distance migrant, traveling as far south as Bolivia. They breed exclusively in North American forests from New York to Missouri. Their migrating range covers most of the southeastern US, while the breeding range only covers parts of Arkansas, Missouri, and Tennessee going upwards. The Carolina’s have a few spots of breeding ranges but is mainly a migrating habitat for the Cerulean Warbler.

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Identification

Cerulean Warblers are small blue birds with two white wingbars and horizontal posture. Males are sky-blue with dark streaking on the back and blue streaking on the sides. Bright white streaks and patches on the wings make them stand out no matter the habitat surrounding them. Females are bluish green with a yellow wash on the underside and whitish eyebrows. The cap of their head has the most bluish hue of their whole body as opposed to the males who are nearly entirely shades of blue. This warbler’s song is a buzzy series of notes that rise in pitch and end in a louder buzzy trill. Male Cerulean Warblers can usually be found singing from high perches in the canopy.

Listen to its song here.

Habitat

This species predominantly breeds in forested areas, in particular temperate mature forests with tall trees of broad-leaved deciduous species. The species may also occupy second-growth forests, varying depending on the region. Many of these birds can either be found in riparian bottomlands (floodplains) or on upper mesic (has a well-balanced supply of moisture) and dry mountain ridge tops more than 500 meters in elevation, but not usually in between. Mesic upland forests that were once occupied by this species are now scarce due to the expansion of farmlands, so it’s likely that this is why these birds sometimes breed in floodplains. Since many of the forests this species historically breeds in either no longer exist or are now scarce, the Cerulean Warbler is considered an area-sensitive species.

There’s much evidence to suggest that this species prefers gaps or openings in the upper canopy, especially in the Appalachians, where an estimated 70% of the Cerulean Warbler population breeds. In this area, male warblers tend to select territories with these canopy gaps on productive slopes, meaning the soil is able to support healthy trees. Female warblers tend to select nest sites with well-spaced, large-diameter trees, increased understory cover, and decreased midstory cover. The preferred nesting trees in the Appalachians are white oak, cucumber magnolia, and sugar maple. Within the Northeast, this species tends to avoid red oak and red maple. The nesting areas of choice may vary in other regions.

Conservation Status 

Status by State

Threats to Conservation

This species is particularly sensitive to landscape changes, so the major threat to the Cerulean Warbler is degradation of habitat through land use change. On breeding grounds, the concerns are wood harvesting in shorter rotation periods, loss of important tree species to disease, and the conversion of mature deciduous forests to agricultural, residential, and urban areas. Most forested landscapes are made up of second growth forests, which lack the complex canopy structure found in old-growth forests preferred by these warblers. Mining in the mountaintops and increased cowbird parasitism also pose known threats to their habitat and nesting efforts.

Funding Opportunities
General Management Guides
Regional Management Guides
Northeast
Midwest & Central
Southeast
Resources
Works Cited