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Guide to North American Birds

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Photo: Kenneth Cole Schneider/Flickr Creative Commons

Priority Bird

Climate Threatened

Black-throated Blue Warbler

Setophaga caerulescens

The lazy, buzzy song of the Black-throated Blue Warbler comes from the undergrowth of leafy eastern woods. Although the bird usually keeps to the shady understory, it is not especially shy; a birder who walks quietly on trails inside the forest may observe it closely. It moves about rather actively in its search for insects, but often will forage in the same immediate area for minutes at a time, rather than moving quickly through the forest like some warblers.

Conservation status	Requires tracts of unbroken forest for nesting, so undoubtedly has declined in some areas. Could be vulnerable to continued loss of habitat in both summer and winter ranges.
Family	Wood Warblers
Habitat	Interior of hardwood and mixed deciduous-coniferous forests. Breeds in large areas of relatively undisturbed forests of maple, birch, beech, eastern hemlock, spruce, and fir; mainly in forest containing a dense undergrowth of shrubs (especially rhododendron bogs) and vine tangles. During migration, tends to be in shrubby or forested places. In winter, inhabits dense tropical woods as well as fence rows and gardens.

Photo Gallery

Feeding Behavior

More methodical in its foraging than many warblers, working over an area thoroughly in the forest understory or lower levels of trees. Forages by gleaning insects among foliage or by hovering briefly to take items from undersurface of leaves. Males tend to forage higher than females in summer. Frequently seen robbing insects from spiderwebs. Will join mixed flocks with other birds on migration and in winter. Establishes winter feeding territories, chasing away others of its own kind.

Eggs

4, sometimes 2-5. Creamy white, with blotches of reddish brown and gray concentrated at larger end. Incubated by female only, 12-13 days. Cowbirds rarely parasitize nests, possibly because this species tends to nest deep in forest interior. Young: Fed by both parents. Young leave nest after 8-10 days, but fly poorly at this stage. Male often becomes sole provider for fledglings, while female begins 2nd or 3rd nest. Female usually becomes main provider for last brood of season. 2 or occasionally 3 broods per summer.

Young

Fed by both parents. Young leave nest after 8-10 days, but fly poorly at this stage. Male often becomes sole provider for fledglings, while female begins 2nd or 3rd nest. Female usually becomes main provider for last brood of season. 2 or occasionally 3 broods per summer.

Diet

Mostly insects. In summer, feeds mostly on insects, especially caterpillars, moths, and crane flies, also spiders. In winter, continues to eat many insects, but also takes seeds, berries, small fruits, and flower nectar. Will visit hummingbird feeders for sugar water.

Nesting

Some males have more than one mate. Pairs are faithful between seasons, 80% of returning birds nest with previous year's mate. Nest site in thick shrubs (such as laurel, alder, rhododendron, viburnum) or saplings, in a fork within 6' of ground, sometimes with leaning dead branch as extra support. Female builds nest, male helps by supplying materials; nest is open cup of bark strips, cobwebs, plants fibers, lined with pine needles, moss, and hair.

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

Migration

Migrates mostly at night. Travels to and from Caribbean mostly via Florida; rare farther west on Gulf Coast. Fall migration often lasts through October, and strays in West may appear even later.

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Migration

Migrates mostly at night. Travels to and from Caribbean mostly via Florida; rare farther west on Gulf Coast. Fall migration often lasts through October, and strays in West may appear even later.

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

Songs and Calls

Song a husky, rising zwee-zwee-zwee.

Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
Learn more about this sound collection.

How climate change could affect this bird's range

In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.

Learn more