MIGRATIONS OF WATERFOWL 



at once (sometimes in an instant if the bird is startled) these ducks of the 

 lakeshore must have some inner stimuli forewarning them to move from 

 their loafing bars to the special molting environment some time before the 

 wing feathers are lost. Indeed, there is evidence of their awareness of the 

 molt: when a Mallard close to the wing molt is flushed, it does not take 

 off in abrupt rise, as normally, but at a more gentle angle, as if favoring the 

 wing against extreme exertion. 



While the molting shift is mostly of males, it is seldom entirely so. The 

 late May and June gatherings often contain a few adult females which, for 

 one reason or another, have abandoned their reproductive attempts for the 

 year. Sometimes, when the hen, thwarted by predators or other adversities, 

 abandons nesting while still attended by a drake, these two maintain their 

 bond as companions and may be seen side by side in the premolting aggre- 

 gations (Sowls, 1949:270). Unsuccessful females, which accompany the 

 males most abundantly during adverse nesting seasons, move with the 

 drakes to their destinations. For the female population as a whole, however, 

 there is no major shift. The evidence suggests that many hens which have 

 raised their broods travel only short distances or remain on the same marsh 

 for the flightless stage. The wing feather molt of the female does not begin 

 until after she has left her family; hence the flightless schedule is much later 

 than it is in the male, some females being flightless in October ( Hochbaum, 

 1944a). 



I have observed no pattern of weather governing the timing of molting 

 shifts, but have noticed that the arrivals and departures of adult drakes in 

 late May and June usually are made in the late afternoon or during twilight. 

 In England Coombes (1950) has made a neat study of the Common Sheld- 

 duck in the act of moving toward its molting place. He found that in July 

 1949 the molt migration "took place on every evening on which visibility 

 from the point of departure was 'good' or perfect,' whereas no migration 

 took place on evenings when visibility was poor or 'bad' . . . Sheld-ducks 

 fly in the worst of weather at sea and along the coast, but are evidently re- 

 luctant to face this overland flight except when visibility and weather are 

 favorable." He found that the migration "takes place during about three 

 hours only, and the great bulk of it is concentrated into two hours, one 

 hour before to one hour after sunset." 



Ward ( 1953 ) gives evidence of a postbreeding movement of adult male 

 Coots from the breeding range to such concentration places as the Delta 

 Marsh, where large numbers pass the flightless season. In the grebes, which, 



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