[order] Passeriformes | [family] Parulidae | [latin] Dendroica castanea | [UK] Bay-breasted Warbler | [FR] Paruline ā poitrine baie | [DE] Braunbrust-Waldsänger | [ES] Chipe Castaņo | [IT] Dendroica pettocastano | [NL] Kastanjezanger

Kastanjezanger determination

copyright: ProAves

A small songbird about 14 cm in length. In breeding plumage, the male has a black face; chestnut crown, throat, and sides; cream-coloured patch on the sides of the neck; a cream-coloured belly; and two bold white wing stripes contrasting with the otherwise dark olive, streaked upperparts. The female is similar in pattern but is significantly duller in colour. In the fall, adult males, females, and young of year have olive green upperparts with two white wing bars and dull yellowish underparts.

Bay-breasted Warblers are found almost exclusively in mature white spruce forest, either in pure stands or mixed with clumps of aspens (Populus tremuloides), birch (Betula papyrifera), and balsam poplar (Populus balsamifera). This species also uses riparian coniferous or mixedwood corridors with multi-layered canopy and frequent openings.

The Bay-breasted Warbler nests in boreal forests, usually with a spruce component, from southeastern Yukon across central Canada to the northern Great Lakes, New England, and Atlantic Canada.

During the breeding season, the Bay-breasted Warbler is a specialized forager, spending most of its time in the shady, interior branches of the middle and upper coniferous canopy. Bay-breasted Warblers are also found in deciduous habitats, foraging at medium to mediumlow heights. Its diet is mainly insectivorous, composed of a variety of adult and larval insects, spiders, and spider and insect eggs. Lepidopteran larvae (e.g., spruce budworms) are the primary food source during the breeding season. The diet switches to mainly fruit during the winter in the tropics when insects are scarce.

This species has a large range, with an estimated global Extent of Occurrence of 2,600,000 km˛. It has a large global population estimated to be 3,100,000 individuals (Rich et al. 2003). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]

The Bay-breasted Warbler is probably seasonally monogamous although mate-switching is possible. Upon arriving on the breeding grounds, males select nesting territories, defending them from conspecific males. The female builds the nest with some assistance from the male. Clutch size ranges from three to seven eggs and is strongly influenced by food supply with larger clutches (six or seven eggs) typical during periods of high food abundance. Eggs are incubated by the female for 12-13 days, nestlings fledge after 10-12 days, and both parents continue to feed young for several days, postfledging. A single brood is raised annually.

It winters from Costa Rica and Panama to Colombia and Venezuela, migrating for the most part across the Gulf of Mexico. Although it nests uncommonly in the lowlands of northeastern British Columbia, east of the Rocky Mountain crest, it is no more than a casual visitor in the rest of the province and the northwestern United States.