The Northern Waterthrush (Parkesia noveboracensis) is one of the larger New World warblers. It breeds in the northern part of North America in Canada and the northern United States including Alaska. This bird is migratory, wintering in Central America, the West Indies and Florida, as well as in Venezuela, Colombia, and Ecuador. It is a very rare vagrant to other South American countries and to western Europe. The Northern Waterthrush is a large New World warbler. It has a length of 12–15 cm (4.7–5.9 in), wingspan of 21–24 cm (8.3–9.4 in) and weigh between 13–25 g (0.46–0.88 oz) Among standard measurements, the wing chord is 6.8 to 8.2 cm (2.7 to 3.2 in), the tail is 4.5 to 5.7 cm (1.8 to 2.2 in), the bill is 1.1 to 1.2 cm (0.43 to 0.47 in) and the tarsus is 1.9 to 2.3 cm (0.75 to 0.91 in). On the head, the crown is brown with a white supercilium. The bill is pointed and dark. The throat is lightly streaked brown to black with heavier streaking continuing onto the breast and flanks. The back is evenly brown. Sexes are morphologically similar. Young birds have buff, rather than white underparts.
The only species bird watchers confuse with the Northern Waterthrush is the closely related Louisiana Waterthrush (Parkesia motacilla, which has buff flanks, a buff undertail, and bright pink legs. The Louisiana Waterthrush also has a whiter throat with fewer streaks. Both waterthrush species walk rather than hop, and seem to teeter, since they bob their rear ends as they move along.