Bird Migration Flyways

Map courtesy Northern Praire Wildlife Research Center

Flyways are heavily traveled routes bird use during migration. During migration, birds tend to follow physical features such as coastlines, mountain ranges and river valleys.

In the 1930's investigators became impressed by what appeared to be four broad, heavily traveled "highways" in North America. This concept was based on several thousand records of migratory waterfowl.

The "highways" were only approximate and many birds migrate outside of them. Since 1948, scientists have designated the four "highways" chiefly to divide the continent into zones for administering laws that deal with the hunting of migratory birds. The four "highways" were applied to other birds as well.

Scientist have gained much more knowledge about bird migration in North America since the 1930's and 1940's. They no longer see the four board migration highways as realistic. The concept of four flyways, designated as the Atlantic, Mississippi, Central and Pacific, are now seen as oversimplifications.

The four highways are only meaningful in a very general way. They are only very generally useful for waterfowl and are not applicable to other birds. Yet the four routes have been useful in managing the hunting of waterfowl.

W.W. Cook identified seven generalized routes for birds leaving the United States on their way to various wintering grounds (see map above). The routes by which birds return northward in the spring are not as well known.

Main Migration Routes in North America

Atlantic Coast Route and Tributaries(route 2)The Atlantic coastline is a regular route of travel. It has many famous birding hotspots 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 by island and mainland to South America. At no time are these air travelers out of sight of land. It is not however the favored migration highway. Only about 25 species of birds use this route to go to their winter homes beyond Cuba to Puerto Rico. This was known as the Atlantic Flyway.

Mackenzie Valley-Great Lakes- Mississippi Valley Routes and Tributaries(route 3)This migration route is the longest of any in the Western Hemisphere. It extends from the Mackenzie Valley past the Great Lakes and down to the Mississippi valley. Its northern end is on the arctic coast in the regions of Kotzebue Sound, Alaska and the mouth of the Mackenzie River. The southern end lies in Argentina. For more than 3,000 miles, from the mouth of the Mackenzie to the Mississippi delta, this route is uninterrupted by mountains. Because it has plenty of trees and water, the area is a great place to view great numbers of migrating birds. During the height of migration, going to birding hotspots in the Mississippi Valley, allow birders to can see large numbers of many species. Swarms of birds are spotted on the islands off the coast of Louisiana. This was known as the old Mississippi Flyway.

(route 4)This route begins in the Mackenzie River delta and Alaska. Some places in this area, such as the National Bison range at Moise, Montana, have food in such abundance that birds stop here during migration to refuel. This was known as the old Central Flyway.

Pacific Coast Route(route 5)The Pacific Coast Route is not as long or heavily traveled as some of the others. Because of the nice living conditions, many species of birds breeding along the coast from the northwestern states up to southeastern Alaska either do not migrate or else make short journeys. This route has its origin chiefly in Western Alaska around the Yukon river delta. Large numbers of arctic-breeding shorebirds also use this route. This was known as the old Pacifc Flyway.

Pacific Oceanic Route (route 6)This route is mainly over water. It extends from the islands of the Bering Strait through the islands of the central Pacific and northward along the Asiatic Coast.Many seabirds that breed in the far northern coasts, southern coasts and islands migrate across the Pacific away from land and except when the breeding season approaches. Incredibly, birds navigate to tiny isolated islands in the middle of the vast Pacific Ocean.

Arctic routes (route 7)Some arctic nesting birds travel only a short distance south in winter. They fly mainly along the coast The best defined arctic route in North America follows the coast of Alaska. Works Consulted

"Migration of Birds: Routes of Migration",http://www.npwrc.usgs.gov/resource/birds/migratio/routes.htm March 09, 2007.

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