Only a single sighting of this bird was made by Audubon during his lifetime. The Chestnut-sided Warbler has benefited and increased in number as abandoned pastures in the northern states have grown up in dense thickets, producing a vast new habitat unavailable when the land was covered with virgin forest.
General: Sexes similar, except female duller in color with less chestnut on sides. 5 inches in length.
Adult Alternate: Black and white striped back. White underparts. Long chestnut line on sides. White face patch surrounded by thick black eyeline and black malar streak. Yellow crown. Two yellow or whitish wing bars. Thin black bill. Black legs.
Basic and Immature: Yellow-green crown, nape and back. Gray face and sides of breast. Dull white belly and undertail coverts. White eye ring. Some chestnut may be visible on sides. Two yellow wing bars. Thin black bill. Black legs.
Young, open woodlands and scrub.
4 white eggs with brown spots. The eggs have a 12-13 day incubation period. Fledging occurs in 10-12 days. The nest is an open cup made from grass and bark and lined with hair and rootlets. The nest is built several feet off the ground in a small tree or bush.