42 CIRCULAR 363, U.S. DEPARTMENT OF AGRICULTURE 
up the Mississippi Valley, and by the early part of June are again on 
their breeding grounds, having performed a round-trip journey in the 
form of an enormous ellipse with the minor axis about 2,000 miles 
and the major axis 8,000 miles, reaching from the Arctic tundras to 
the pampas of Argentina. The older birds are probably accompanied 
by some of the young, perhaps those from early nestings, but most 
of the immatures leave their natal grounds late in summer and move 
southward through the interior of the country, returning in spring 
over essentially the same course. The elliptical route is therefore 
used chiefly by fully adult birds. 
ATLANTIC COAST ROUTE AND TRIBUTARIES 
The Atlantic coast is a regular avenue of travel, and along it are 
many famous points for observing both land and water birds. About 
50 different kinds of land birds that breed in New England follow 
the coast southward to Florida and travel thence by island and main- 
land to South America (fig. 20, route 2). As will be seen from the 
map, a seemingly natural and convenient highway extends through 
the Bahamas, Cuba, Hispaniola, Puerto Rico, and the Lesser 
Antilles to the South American coast. Resting places are afforded at 
convenient intervals, and at no time need the aerial travelers be out 
of sight of land. It is not, however, the favored highway, and only 
about 25 species of birds go beyond Cuba to Puerto Rico along this 
route to their winter quarters, while only 6 species are known to 
reach South America by way of the Lesser Antilles. The obvious 
drawback is lack of adequate food. The total area of all the West 
Indies east of Puerto Rico is less than that of Rhode Island, so that 
if only a small part of the birds of the eastern United States were to 
travel this way, it is doubtful whether even the luxuriant flora and 
fauna of tropical habitats would provide food sufficient for their 
needs. 
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 
erounds 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, red- 
heads, 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 moun- 
tains, 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 
