At a Glance
The sky-blue upperparts of the male Cerulean Warbler are difficult to observe in summer: At that season, the birds stay high in the tops of leafy trees in the eastern United States and extreme southern Canada. The bird itself has become harder to observe in recent decades, as its numbers have decreased in parts of its range. Cowbirds, which lay their eggs in the warblers' nests, may be finding their unwitting 'hosts' more easily as forest patches become smaller.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Perching Birds, Wood Warblers
Forests and Woodlands, Freshwater Wetlands
California, Eastern Canada, Florida, Great Lakes, Mid Atlantic, New England, Plains, Southeast, Texas
Direct Flight, Flitter
Range & Identification
Migration & Range Maps
Moves south relatively early in fall. Spring migrants coming north from South America may make a regular stopover in Belize before continuing north across the Gulf of Mexico to southeastern United States. A very rare stray anywhere in west.
4 1/2" (11 cm). Adult male is only tiny bird with blue back, white throat, black necklace. Female and young duller; have sharp white wing-bars, pale eyebrow, hint of blue on back.
About the size of a Robin, About the size of a Sparrow
Black, Blue, Gray, White
Songs and Calls
Series of short buzzy notes, followed by a higher-pitched buzz.
Buzz, Chirp/Chip, Hi, Trill, Whistle
Deciduous forests, especially in river valleys. Breeds in mature hardwoods either in uplands or along streams. Prefers elm, soft maple, oak, birch, hickory, beech, basswood, linden, sycamore, or black ash. Nests only in tall forest with clear understory. In winter in tropics, found mostly in forest and woodland borders in foothills and lower slopes.
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3-5, usually 4. Gray or creamy off-white, with spots of brown. Incubation by female only, probably 12-13 days. Apparently does not often host cowbird eggs where it can nest in unbroken mature forest, but may be parasitized more frequently in forest fragments. Young: Both parents feed the nestlings. Age at which the young leave the nest is not well known.
Both parents feed the nestlings. Age at which the young leave the nest is not well known.
Forages mostly high in trees, moving rapidly from limb to limb, searching among foliage and twigs for insects. Also flies out to catch flying insects in mid-air. In winter in the tropics, scattered individuals forage with mixed flocks, ranging from low to high in the trees.
Insects. The diet is not well known; undoubtedly feeds mostly or entirely on insects, like most warblers. Has been observed feeding on caterpillars.
Males arrive on breeding grounds near the middle of May. Nesting behavior has been little studied, owing to the difficulty of observing the nests. Nest: Placed on horizontal branch of hardwood, far from trunk and usually high, 15-90' up in tree. Favors oak, maple, basswood, elm, hickory, sycamore, beech, or tulip trees. Nest is a small, shallow open cup (probably built by female), made of bark strips, grasses, weeds, spider silk, and lichen; lined with moss and hair.
Possibly threatened or endangered. Surveys show strongly declining numbers in recent years. Nesting efforts may fail because of increasing cowbird parasitism in smaller patches of forest. May also be losing wintering habitat in tropics.
Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect the range of the Cerulean Warbler. Learn even more in our Audubon’s Survival By Degrees project.
Climate Threats Facing the Cerulean Warbler
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.