Photo: Glenn Bartley/Vireo

Bay-breasted Warbler

Setophaga castanea

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."
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.
Family Wood Warblers
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.
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."
Photo Gallery
  • adult male, breeding
  • adult female, breeding
  • immature female (1st summer)
  • adult male, nonbreeding
  • adult male, breeding
  • adult female and nestlings
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.


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.


Young

Both parents feed the nestlings. Young leave the nest 11-12 days after hatching.

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.

Illustration © David Allen Sibley.
Learn more about these drawings.

Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

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.

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Migration

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.

  • All Seasons - Common
  • All Seasons - Uncommon
  • Breeding - Common
  • Breeding - Uncommon
  • Winter - Common
  • Winter - Uncommon
  • Migration - Common
  • Migration - Uncommon
Songs and Calls
A high thin teesi-teesi-teesi-teesi, without change in pitch or volume.
Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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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

Read more: climate.audubon.org
Wood Warblers Perching Birds

Bay-breasted Warbler

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season.

More on reading these maps.

Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”

The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).

The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.

The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.

The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.

You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.
Winter
Summer

Winter Range
Summer Range
Both Seasons
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