Chestnut-sided Warbler Identification

Adult Description

  • Small songbird.
  • Forehead yellow.
  • Black mustache stripe on face.
  • Underparts white.
  • Chestnut streak along sides.

Male Description

Breeding (Alternate) plumage: Crown bright yellow, with white edge at front. Nape pale gray streaked with black. Back striped yellow and black. Tail blackish. Black stripe from bill to behind eye. Black mustache stripe. Cheek white. Throat, chest, belly, and under tail white. Sides with long narrow chestnut streak. Two broad yellowish wingbars. Flight feathers outlined in pale yellow or white.
Nonbreeding (Basic) plumage: Back, nape, and crown yellowish green. Some dark streaking on rump. Sides of head and neck pale gray. White eyering. Underparts dull white. Long thin streak of chestnut along sides. Two broad yellowish wingbars. Flight feathers outlined in pale yellow or white. Eyes dark. Legs dark.

Female Description

Breeding (Alternate) plumage: Chestnut streak on sides less extensive than on male. Wings with two broad yellowish wingbars. Crown greenish yellow. Dull black or slaty line through eye. Dull black or slaty mustache stripe. Cheek whitish. Back green with black streaks.
Nonbreeding (Basic) plumage: Back, nape, and crown yellowish green. Some dark streaking on rump. Sides of head and neck pale gray. White eyering. Underparts dull white. Thin streak of chestnut along sides; may be absent. Two broad yellowish wingbars. Flight feathers outlined in pale yellow or white. Eyes dark. Legs dark.

Immature Description

Immature resembles fall adult, but streaks on back finer. Immature female without chestnut on sides.
Relative Size

Relative Sizesparrow or smallersparrow-sized or smaller
Measurements
  • Both Sexes
    • Length: 3.9-4.3 in (10-11 cm)
    • Wingspan: 7.1-8.3 in (18-21 cm)