They usually leave the nest on the tenth or eleventh day and move to low open thickets where they wait to be fed. The chestnut-sided warbler is believed to be monogamous. It is highly territorial during the breeding season. It is a nocturnal migrant. During migration, it may join other flocks and occasionally forage with them.
Males produce two song classes.
The first is used before the arrival of the females and in the early nesting cycle. The second is used while raising young. Habitat Before the 1800s, the chestnut-sided warbler was not well known. Because of its highly specialized habitat and foraging techniques, it was believed to be limited to former natural disaster areas such as sites of forest fires. With the clearing of primeval forests and the subsequent growth of shrubby habitats, the chestnut-sided warbler is one of the most abundant breeding warblers in second growth deciduous woodlands.