Appearance
The summer male bay-breasted warblers are unmistakable. They have grey backs, black faces, and chestnut crowns, flanks and throats. They also boast of bright yellow neck patches, and their underparts are white. They have two white wing bars, as well.Breeding females essentially resemble washed out versions of the male. The females are greyish above and white below, with much weaker head patterns. The females also only have chestnut markings on small flank patches, although tiny tints in their grey crowns have been observed.
Non-breeding birds have greenish heads, greenish upperparts and yellowish breasts. The yellow extends to the belly of young birds. The two white wing bars are always present in every stage of life. These birds differ from non-breeding blackpoll warblers in the absence of breast streaks.
Naming
The genus name ''Setophaga'' is from Ancient Greek ''ses'', "moth", and ''phagos'', "eating", and the specific ''castanea'' is Latin for chestnut-coloured.Behavior
Their songs are a repetitive high-pitched ''si si si''.Reproduction
Their breeding habitats are coniferous woodlands. Bay-breasted warblers nest 5–20 ft up in conifer trees, laying 3–5 eggs in a cup-shaped nest. Incubation is 12 days. More eggs are laid in spruce budworm years.Food
These birds feed on insects, and the numbers of these birds vary with the abundance of the spruce budworm. These birds will also feed on berries and nectar in wintertime.References:
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