Breeding male. Note: yellow crown, white cheeks, and extensive chestnut flanks.
  • Breeding male
  • Breeding male. Note: yellow crown, white cheeks, and extensive chestnut flanks.
  • Breeding male
  • Breeding female. Note: less demarcated malar and less extensively chestnut flanks.
  • Nonbreeding male. Note: plain gray face and faint chestnut sides.
  • Juvenile. Note: white eye ring, gray underparts, and pale bill.

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Chestnut-sided Warbler

Dendroica pensylvanica
Members of this diverse group make up more than half of the bird species worldwide. Most are small. However their brains are relatively large and their learning abilities are greater than those of most other birds. Passerine birds are divided into two suborders, the suboscines and the oscines. Oscines are capable of more complex song, and are considered the true songbirds. In Washington, the tyrant flycatchers are the only suboscines; the remaining 27 families are oscines.
This large group of small, brightly colored songbirds is a favorite of many birdwatchers. Wood-warblers, usually called “warblers” for short by Americans, are strictly a New World family. Most of the North American members of this group are migratory, returning in the winter to the tropics where the family originated. Warblers that nest in the understory tend to have pink legs and feet, while those that inhabit the treetops usually have black legs and feet. North American males are typically brightly colored, many with patches of yellow. Most North American warblers do not molt into a drab fall/winter plumage; the challenge posed to those trying to identify warblers in the fall results from looking at mostly juvenile birds. Their songs are generally dry, unmusical, often complex whistles (“warbles”). Warblers that live high in the treetops generally have higher-pitched songs than those that live in the understory. Warblers eat insects gleaned from foliage or captured in the air. Many supplement their insect diet with some seeds and fruit, primarily in fall and winter, and some also eat nectar. Most are monogamous. The female usually builds the nest and incubates four to five eggs for up to two weeks. Both members of the pair feed the young.

    General Description

    Breeding adults have a yellowish crown, black eye line and mustache mark, dark wings with two pale-yellow wing-bars, chestnut on the sides, white underparts, and a streaked back. Immature (first-fall) birds are much plainer, with a greenish crown and back, gray underparts, and a prominent white eye-ring. Fall adults are similar to immatures but usually show some chestnut on the sides.

    Chestnut-sided Warblers nest in forests from eastern Alberta across southern Canada to Nova Scotia, the upper Midwest and northeastern U.S., and southward along the Appalachian spine. They winter in southern Mexico and Central America, migrating mostly east of the Great Plains and in direct flight across the Gulf of Mexico. However, this is one of the commoner “eastern” warblers encountered in the West. British Columbia has many records from all regions of the province, including confirmed breeding. Idaho has about 30 records equally divided between spring and fall. The species occurs just about annually in Oregon, with spring records outnumbering fall records by about 3:1. Washington shows a similar early-season bias, with 14 of 17 accepted records in June and the first half of July and the remaining three from late August to October. Twelve of these records are from east of the Cascade crest and five are from the westside lowlands.

    Revised October 2007

    North American Range Map

    North America map legend

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