Bay-breasted Warbler
Bay-breasted Warbler
Setophaga castanea
At a Glance
This is a characteristic warbler of spruce forest in eastern Canada in summer. Its numbers vary from year to year, and are likely to increase quickly during population explosions of the spruce budworm or other forest pests. This species forages rather slowly compared to most warblers, moving deliberately among the branches. The male Bay-breasted Warbler is unmistakable in spring but goes through a striking transformation in fall, becoming a greenish 'confusing fall warbler.'
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.
Category
Perching Birds, Wood Warblers
IUCN Status
Least Concern
Habitat
Forests and Woodlands, Shrublands, Savannas, and Thickets, Tundra and Boreal Habitats
Region
California, Eastern Canada, Florida, Great Lakes, Mid Atlantic, New England, Plains, Rocky Mountains, Southeast, Southwest, Texas, Western Canada
Behavior
Direct Flight, Flitter
Population
9.900.000
Range & Identification
Migration & Range Maps
In spring, most apparently move north through Central America and then fly north across the Gulf of Mexico, continuing to Canada and the Northeast. In fall, evidently moves south on a broader front. Some may linger quite late in fall.
Description
5 1/2" (14 cm). Spring male has head/chest pattern of chestnut, black, and buff. Spring female paler, usually has hint of same pattern. Fall birds very much like fall Blackpoll Warbler but undertail coverts usually buff (not white), chest lacks blurry streaking, sides of neck brighter greenish, legs always dark (some fall Blackpolls have yellow legs). See Pine Warbler.
Size
About the size of a Sparrow
Color
Black, Green, Red, Tan, White, Yellow
Wing Shape
Rounded
Tail Shape
Notched, Square-tipped
Songs and Calls
A high thin teesi-teesi-teesi-teesi, without change in pitch or volume.
Call Pattern
Flat, Undulating
Call Type
Chirp/Chip, Hi, Whistle
Habitat
Woodlands, conifers in summer. Usually breeds in northern coniferous forest, in thick stands of spruce and fir. Where spruce is not found, will nest in deciduous or mixed second-growth woods of birches, maples, firs, and pines. In winter in the tropics, occurs in forest edge, second growth, and open woodland.
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Behavior
Eggs
4-5, sometimes 3-7. Off-white, with brown or black marks at larger end. Incubated by female, 12-13 days. Female is fed on the nest by the male during incubation. Tends to lay more eggs in years of spruce budworm outbreaks, when food is abundant. Rarely parasitized by cowbirds.
Young
Both parents feed the nestlings. Young leave the nest 11-12 days after hatching.
Feeding Behavior
Appears more sluggish in foraging than do other Dendroica warblers feeding in the same spruce forests. Forages in and out along branches, mostly at mid-levels in trees. Rarely catches flying insects in mid-air. In winter in the tropics, joins mixed foraging flocks in the forest canopy.
Diet
Mostly insects, berries. In breeding season, eats a variety of insects, including beetles, flies, moths, caterpillars, leafhoppers, and grasshoppers; also Virginia creeper berries and mulberries. May eat many spruce budworms when that insect is at epidemic numbers. In winter in the tropics, also eats many berries.
Nesting
Males may not arrive on breeding grounds until early June. Nest site is on a horizontal branch of a dense spruce, hemlock, birch, or other tree, 4-40' above the ground. Nest is a large, open cup, either loosely built or compact, made of grasses, lichens, roots, mosses, and protruding conifer twigs; lined with bark strips and hair.
Climate Vulnerability
Conservation Status
Numbers may rise and fall, increasing after big outbreaks of spruce budworm or other insects. Could be vulnerable to loss of habitat on wintering grounds.
Climate Threats Facing the Bay-breasted 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.