MIGRATIONS OF WATERFOWL 



gunning with a companion ; and when an area is vacated by ducks in mass 

 migration, adults and juveniles inevitably are companions. 



This ratio of adults to juveniles varies from year to year because of vari- 

 ations in reproductive success (Hickey, 1952), but in an annual breakdown 

 of the Delta bags, and in the more recent bag examinations (Weller, 1953b), 

 there continues a strong element of adult birds. 



It is this regular adult component of the population that must be, I 

 believe, the directive element in the mass autumn migrations. These pas- 

 sages are precise, deliberate, orderly, and oriented because of the presence of 

 the experienced birds. This is social orientation in which the actions of the 

 experienced set the direction for all. In these grand avalanches, with thou- 

 sands of birds and hundreds of flocks, each within sight of another, the 

 individual bird, like a private in a parade, moves with and as his com- 

 panions. The flock is the individual, "a collective bird, in fact, and however 

 stretched, straggling and complicated . . . the individual element seems 

 wonderfully in abeyance" (Selous, 1931:127). 



Without documenting the discussion further, it seems fair to arrive at 

 five conclusions regarding the fall migration of waterfowl : 



1. Massive movements of many flocks of ducks traveling at the same 

 time in the same direction are annual events. 



2. The standard direction of these mass flights holds the same from 

 year to year. 



3. These migrations sweeping vast numbers of ducks down the flyways 

 are regional in character, the shift southward being spread over a range that 

 is wide and deep. 



4. Adult and juvenile ducks travel together in these movements. 



5. These passages obey topographic features such as lakes, marshes, and 

 rivers when these lead toward the wintering grounds, overland routes being 

 followed when there is no direct watercourse. 



Visual observations tell of the regularity of these major movements in 

 both place and direction, but show nothing of the fidelity of individual 

 birds to the trails. Does a duck come each autumn to the same places along 

 the way of migration ? The answer is to be found in the records of banding 

 stations, and there is no need to go further than McGinnis Slough for evi- 

 dence. This is a small lake within twenty-one miles of Chicago's loop. Here, 

 with wise foresight, the Cook County Forest Preserve has created an im- 

 portant, if small, stopping place for waterfowl moving down the Mississippi 

 Flyway; and here were banded some 26,415 ducks and coots during the 



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