This flyway is relatively simple although it presents some features of interest, chiefly as they affect the migratory waterfowl. It's eastern boundary runs through the peninsula of southern Ontario to western Lake Erie, then southwestwardly across Ohio and Indiana to the Mississippi where it rather closely follows the river to its mouth. The western boundary does not have such precise definition as the eastern boundary, and for this reason in eastern Nebraska and western Missouri and Arkansas the Mississippi Flyway merges imperceptibly into the Central Flyway. The longest migration route of any in the Western Hemisphere lies in this flyway. It's northern terminus is on the Arctic coast of Alaska and its southern end in Patagonia. During the spring migration some of the shorebirds traverse the full length of this great artery and several species that breed north to Yukon and Alaska must twice each year cover the larger part of it. For more than 3000 miles, from the mouth of the Mackenzie to the delta of the Mississippi, this route is uninterrupted by mountains. There is not even a ridge of hills on the entire route that is high enough to interfere with the movements of migrating birds, and the greatest elevation above sea level is less than 2000 feet. Well timbered and watered, the entire region affords ideal conditions for the support of hosts of migrating birds. The two rivers that mark it, the Mackenzie emptying on the Arctic coast and the Mississippi in the Gulf of Mexico, have a general north-and-south direction, another factor in determining the importance of this route which is used by large numbers of ducks, geese, shorebirds, blackbirds, sparrows, warbler and thrushes,
The majority of North American land birds, seeking winter homes in the tropics, that come south through the Mississippi Flyway take the short cut across the Gulf of Mexico in preference to the longer, though presumably safer, land or island journey by way of Texas or the Antilles. During the height of migration some of the islands off the coasts of Louisiana and Texas are wonderful observation places.
It was once thought that most of the North American birds that migrate to Central America made a leisurely trip along the west coast of Florida, crossed to Cuba and then made the short flight from the western tip of that island to Yucatan. The map will suggest this as the most natural route, but as a matter of fact, it is used by only certain swallows and shorebirds, or an occasional individual of some other species that has been driven from its accustomed course.