regard to migration pathways for even a single species let alone 

 waterfowl in general. 



Flyways and Corridors 



Through plotting accumulated banding data in the 1930's, 

 investigators became impressed by what appeared to be four broad, 

 relatively exclusive flyway belts in North America. This concept, 

 based upon analyses of the several thousand records of migratory 

 waterfowls recoveries then available, was described by Lincoln 

 (1935a). In this paper (p. 10), Lincoln concluded that: 



. . . because of the great attachment of migratory birds for 

 their ancestral flyways, it would be possible practically to 

 exterminate the ducks of the West without seriously interfer- 

 ing with the supply of birds of the same species in the Altantic 

 and Mississippi flyways, and that the birds of these species 

 using the eastern flyways would be slow to overflow and re- 

 populate the devasted areas of the West, even though environ- 

 mental conditions might be so altered as to be entirely 

 favorable. 



Since 1948, this concept served as the basis for administrative action 

 by the Fish and Wildlife Service in setting annual migratory water- 

 fowl hunting regulations. 



The concept of bird populations being confined to four fairly 

 definite and distinct migration "flyways" is probably most applicable 

 to those birds that migrate in family groups, namely geese, swans, 

 and cranes, but does not appear to be very helpful in understanding 

 the movements of the more widely dispersing ducks. The "pioneering 

 spirit" in Canada geese, for example, is limited by their social 

 structure the young travel to and from specific breeding and 

 wintering areas with their parents. These young later in life usually 

 breed in the same areas as did their parents. If a goose population is 

 decimated in one flyway, either by hunting or natural calamities, 

 other goose populations in other flyways are not seriously 

 endangered, but also these populations are very slow to repopulate an 

 area where the previous goose population had been decimated. This is 

 not the case with ducks because these birds are not always bound by 

 their intrinsic behavior to return to specific breeding areas. Con- 

 sequently, vacant breeding areas are more rapidly repopulated by 

 ducks than by geese. 



Although Lincoln's analysis was confined to ducks and geese, some 

 thought that it applied to other groups of birds as well. Everyone 

 now realizes that the concept of four flyways, designated as the 

 Atlantic, Mississippi, Central, and Pacific Flyways, was an 

 oversimplification of an extremely complex situation involving 

 crisscrossing of migration routes, varying from species to species. It 

 can be considered meaningful only in a very general way, even for 

 waterfowl, and not applicable generally to other groups of birds. 

 Nevertheless the four "Flyway" areas have been useful in 



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