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 landbirds that breed in New England follow the coast southward to Florida and travel thence by island and mainland to South America ([Fig. 18.], route 2). The map indicates a natural and convenient highway 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; only about 25 species of birds go beyond Cuba to Puerto Rico along this route to their winter quarters, while only six species are known to reach South America by way of the Lesser Antilles. Many thousands of American coots and wigeons, pintails, blue-winged teal, and other waterfowl as well as shorebirds, regularly spend the winter season in the coastal marshes, inland lakes, and ponds of Cuba, Hispaniola, and Puerto Rico.
Route No. 3 ([Fig. 18.]) is a direct line of travel for Atlantic coast migrants en route to South America, although it involves much longer flights. It is used almost entirely by landbirds. After taking off from the coast of Florida there are only two intermediate land masses where the migrants may pause for rest and food. Nevertheless, tens of thousands of birds of about 60 species cross the 150 miles from Florida to Cuba where many elect to remain for the winter months. The others negotiate the 90 miles between Cuba and Jamaica, but, from that point to the South American coast, there is a stretch of islandless ocean 500 miles across. Relatively few North American migrants on this route go beyond Jamaica. The bobolink so far outnumbers all other birds using this route that it may be designated the "bobolink route" ([Fig. 19.]). As traveling companions along this route, the bobolink may meet vireos, kingbirds, and nighthawks from Florida, Chuck-will's-widows from the Southeastern States, black-billed and yellow-billed cuckoos from New England, gray-cheeked thrushes from Quebec, bank swallows from Labrador, and blackpoll warblers from Alaska. Sometimes this scattered assemblage will be joined by a tanager or a wood thrush, but the "bobolink route" is not popular with the greater number of migrants.
Figure 19. Distribution and migration of the bobolink. In crossing to South America, most of the bobolinks use route 3 ([Fig. 18.]), showing no hesitation in making the flight from Jamaica across an islandless stretch of ocean. It will be noted that colonies of these birds have established themselves in western areas, but in migration they adhere to the ancestral flyways and show no tendency to take the short cut across Arizona, New Mexico, and Texas.
Formerly, it was thought most North America landbirds migrated to Central America via the Florida coast, then crossed to Cuba, and finally made the short flight from the western tip of Cuba to Yucatan. A glance at the map would suggest this as a most natural route, but, as a matter of fact, it is practically deserted except for a few swallows and shorebirds or an occasional landbird storm-driven from its normal course. What actually happens in the fall is that many of the birds breeding east of the Appalachian Mountains travel parallel to the seacoast in a more or less southwesterly direction and, apparently maintaining this same general course from northwestern Florida, cross the Gulf of Mexico to the coastal regions of eastern Mexico. They thus join migrants from farther inland in using route No. 4 ([Fig. 18.]).
Routes used by the Atlantic brant merit some detail because their flight paths were long misunderstood. These birds winter on the Atlantic coast, chiefly at Barnegat Bay, New Jersey, but depending upon the severity of the season and the food available, south also to North Carolina. Their breeding grounds are in the Canadian arctic archipelago and on the coasts of Greenland. According to the careful studies of Lewis (1937), the main body travels northward in spring along the coast to the Bay of Fundy, overland to Northumberland Strait, which separates Prince Edward Island from mainland New Brunswick and Nova Scotia. A minor route appears to lead northward from Long Island Sound by way of the Housatonic and Connecticut River Valleys to the St. Lawrence River.
After spending the entire month of May feeding and resting in the Gulf of St. Lawrence, the eastern segment of the brant population resumes its journey by departing overland from the Bay of Seven Island area. The eastern and larger segment of the population appears to fly almost due north to Ungava Bay and from there to nesting grounds, probably on Baffin Island and Greenland. The smaller segment travels a route slightly north of west to the southeastern shores of James Bay, although east of that area some of the flocks take a more northwesterly course by descending the Fort George River to reach the eastern shore of James Bay. Upon their arrival at either of these two points on James Bay, the brants of this western segment turn northward and proceed along eastern Hudson Bay to their breeding grounds in the Canadian Arctic.
In general, the fall migration of the brant follows the routes utilized in the spring. At this season, the eastern population appears only on the western and southern shores of Ungava Bay before continuing their southward journey to the Gulf of St. Lawrence and beyond. Also, it appears that most of the birds of the western segment, instead of following the eastern shores of Hudson and James bays, turn southwestward across the former, by way of the Belcher Islands, to Cape Henrietta Maria, and from there south along the western shores of James Bay by way of Akimiski and Charlton Islands. At the southern end of James Bay, they are joined by those that have taken the more direct route along the east coasts of the bays and all then fly overland 570 miles to the estuary of the St. Lawrence River.
The Atlantic coast wintering area 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, redheads, scaup, Canada geese, and many black ducks that winter in the waters and marshes of the coastal region south of Delaware Bay. The canvasbacks, redheads, and scaup coming from breeding grounds on the great northern plains of central Canada follow the general southeasterly trend of the Great Lakes, 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 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 the St. Clair Flats between Michigan and Ontario, swing abruptly to the southeast and cross the mountains to reach the Atlantic coast south of New Jersey. This route, with its Mississippi Valley branch, has been fully documented by the recovery records of ducks banded at Lake Scugog, Ontario.
Canvasbacks migrate from the prairie pothole country of the central United States and Canada to many wintering areas in the United States. This duck has been the subject of a particular study (Stewart, Geis, and Evans 1958), and its principle migration routes, based on recovery of banded birds, are shown to follow an important trunk route from the major breeding area in the prairie provinces of Canada and the northern prairies of the United States southeastward through the southern Great Lakes area to Chesapeake Bay, the chief wintering area ([Fig. 20.]). Relatively few canvasbacks proceed southward along the Atlantic seaboard. A less important route branches off from the main trunk in the southern Minnesota region and extends south along the Mississippi Valley to points along the river. Other individuals of the prairie breeding population fly southward on a broad front to the gulf coast of Texas and the interior of Mexico, while some proceed southwestward on a relatively broad path to the northern Pacific coast.