The male selects the general area of the nesting site, but the female chooses the actual nest site. Nests are usually in the cavity of a root system of wind-blown trees in a wooded swamp, on the side of a fern clump or under cover along the banks of a lake or a river. There is typically covering above the nest and an opening to one side. The exterior of the nest is mainly moss and liverwort gametophytes. The interior of the nest cup is constructed with grass stems, twigs, or pine needles, and then lined with the hair of deer, caribou, cow, and rabbit.
Average clutch is composed of four white ovate eggs spotted with browns and greys.
The female is solely responsible for incubation, which lasts 12 days. Both parents, however, share feeding responsibilities. Behavior The Northern Waterthrush is solitary before pair formation, then forms family groups after the young depart from the nest. The bird is an annual migrant to the West Indies and Central and South America. Migrations are made in loosely associated flocks that fly at night.