In the northern part of the Atlantic coast route is a tributary route used by the brant (_Branta bernicla_) that is of special interest. The southward movement of these birds is chiefly along the western shores of Hudson Bay and thence southeastward to the Atlantic coast. Returning in spring, they follow the coast line north to the Gulf of St. Lawrence and then fly almost due north to their breeding grounds on the west coast of Greenland and the islands of the Arctic archipelago. The round trip is therefore in the form of a great ellipse, probably 3,000 miles long by 1,000 miles wide. The Atlantic flyway receives accretions of waterfowl from three or four interior migration paths, one of which is of first importance, as it includes great flocks of canvasbacks (_Nyroca valisineria_), redheads (_N. americana_), scaup ducks (_N. marila_ and _N. affinis_), Canada geese, and many of the black ducks that winter in the waters and marshes of the coastal region south of Delaware Bay. The canvasbacks, redheads, and scaups come from their breeding grounds on the great northern plains of central Canada, follow the general southeasterly trend of the Great Lakes (fig. 21), cross Pennsylvania over the mountains, and reach the Atlantic coast in the vicinity of Delaware and Chesapeake Bays. Black ducks, mallards, and blue-winged teals (_Querquedula discors_) that have gathered in southern Ontario during the fall leave these feeding grounds and proceed southwest over a course that is apparently headed for the Mississippi Valley. Many do continue this route down the Ohio Valley, but others, upon reaching the vicinity of Lake St. Clair, between Michigan and Ontario, swing abruptly southeast and, crossing the mountains in a single flight, reach the Atlantic coast south of New Jersey. This route, with its Mississippi Valley branch, has been fully demonstrated by the recovery records of ducks banded by a cooperator of the Biological Survey at Lake Scugog, Ontario. The white-winged scoter (_Melanitta deglandi_), which also breeds in the interior country from northern North Dakota north to the Arctic coast, is another bird having an elliptical migration route, so far as those wintering on the Atlantic coast are concerned. This duck breeds only near fresh water and winters entirely on the ocean along both the Atlantic and Pacific coasts of the United States. Those wintering on the Atlantic side leave their breeding grounds west of Hudson Bay and fly 1,500 miles almost due east to the most eastern part of Labrador, whence they proceed southward across the Gulf of St. Lawrence to their winter home, which extends from southwestern Maine to Chesapeake Bay. The spring flight is made by an interior route that traverses the valleys of the Connecticut, Hudson, and Ottawa Rivers, and thence passes west and north to the breeding grounds.