MIGRATIONS OF WATERFOWL 



appetites are consummated. The distance of homeward migration in ducks 

 varies from a few miles for some individuals which nest near their winter 

 range, to several thousand miles for others of the same species. In ducks 

 which take new mates each year, the destination depends upon the experi- 

 ence of the female returning to her home range. In geese and swans, which 

 mate for life, the pair annually returns to its familial breeding grounds. In 

 ducks, parents and children (which in many species are ready to breed their 

 first spring) are not together as family groups, having separated the previous 

 summer. In geese and swans the homeward-bound adults are accompanied 

 by their yearling children. In the Northern Hemisphere this sexual migration 

 toward the nesting place may begin as early as January for some individuals, 

 while others do not gain their breeding grounds until June. Birds nesting at 

 the southern edge of the breeding range may have young before others of 

 the same species have arrived on nesting places in the extreme north. 



The homeward migration of cranes is like that of the geese and swans. 

 Some other birds, like the Crow and the Barn Swallow, reach their nesting 

 place in pairs, as do many ducks ; but I do not know whether the female so 

 strongly directs the course of migration as in ducks. The pattern in water- 

 fowl, of course, is very different from that in many passerine birds, such as 

 the Red-winged Blackbird (Allen, 1914), in which the male returns to his 

 breeding territory before the female. 



The impetus of homeward migration is sexual, but the exact schedule, by 

 days or weeks, is modified by the weather, with the heaviest spring passages 

 occurring "during the interval between the passage of a warm front through 

 the region and the subsequent arrival of a cold front" (Bagg et al, 1950). 



Mass fall migration 



Mass fall migration is the act of experienced birds retracing their steps, 

 usually over standard directions in direct passage from the breeding or 

 molting range to the wintering grounds or to traditional stopping places 

 along the way. Mass fall migrations begin in August, after the adult males 

 have completed their flightless period of the eclipse molt, and they continue 

 through the autumn till the final evacuation from the breeding grounds with 

 the arrival of deep frost. Mass movements may be made up entirely of adult 

 males of one species, as in the post-molt flight of adult drake Pintails, or they 

 may be composed of all sex and age classes, with several or many species 

 represented. When a number of species move in mass, each kind, neverthe- 

 less, holds to flocks of its own in which juveniles and adults are usually to- 



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