Guide to North American Birds

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Adult male. Photo: Frode Jacobsen/Shutterstock

Priority Bird

Cerulean Warbler

Setophaga cerulea

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.

Conservation status	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.
Family	Wood Warblers
Habitat	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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Feeding Behavior

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.

Eggs

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.

Young

Both parents feed the nestlings. Age at which the young leave the nest is not well known.

Diet

Insects. The diet is not well known; undoubtedly feeds mostly or entirely on insects, like most warblers. Has been observed feeding on caterpillars.

Nesting

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.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

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.

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Migration

All Seasons - Common
All Seasons - Uncommon
Breeding - Common
Breeding - Uncommon
Winter - Common
Winter - Uncommon
Migration - Common
Migration - Uncommon

Songs and Calls

Series of short buzzy notes, followed by a higher-pitched buzz.

Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How Climate Change Will Reshape the Range of the Cerulean Warbler

Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.

Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.

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.