The Swamp Sparrow’s nest is a bulky open cup, about four inches in diameter, made of dry grasses, sedges, plant stalks and leaves, and lined with fine grass, plant fibers and occasionally hair. Some nests are placed on the ground, but most are located about a foot above water in dense cattails, grass or shrubs.
The clutch size is typically 4-5 eggs, bluish green in color with brown spots and blotches. Females incubate the eggs 12-14 days, and chicks fledge 9-11 days after hatching. Birds that nest in the southern part of the breeding range, including the Great Lakes region, usually raise two broods per year.