MIGRATIONS OF WATERFOWL 



seen arriving migrants in flocks of fifty or sixty, sometimes even a hundred 

 or more birds. The individual components of these big companies show 

 themselves when they begin their long, shallow descent to the marsh. Then 

 the body of travelers breaks up into smaller groups, each making its inde- 

 pendent arrival at Delta. 



Waterfowl reach Delta from two main directions (Figure 16). Some 

 come from the southeast, their source being precisely the same direction 

 into which they departed in the mass migrations of autumn. Others come 

 from due south. I do not know which of these directions produces the 

 greatest flow of spring arrivals, but I believe most of the waterfowl come 

 from the southeast. Surely all the Whistling Swans and most of the diving 

 ducks are from that direction. 



In their evening departure, most ducks start out into the northwest to 

 a point of the compass that is the same whence they arrived in autumn. Not 

 all, however, are committed to this standard direction, and flocks some- 

 times may be seen breaking away to the north. Whistling Swans, like most 

 of the ducks, migrate into the northwest; Canada Geese go northwest, north, 

 or north-northeast; Richardson's Geese head north or north-northeast. In 

 their mass movement away from the prairie country, the Blue Geese and 

 the Lesser Snow Geese invariably fly to the same point of the compass in 

 the east-northeast (Figure 16). 



Ducks reaching Delta in spring have their March and April rendezvous 

 in Minnesota and northeastern North Dakota. There, on the lake and marsh 

 country of the prairies, waterfowl from the east coast meet those of the 

 Mississippi Valley. Smith (1946) found that most Canvasbacks migrating 

 through Minnesota make their spring headquarters in the lake region about 

 Ashby, their heaviest numbers occurring on Lake Christina (Figure 16). On 

 April 4, 1942, he counted 2,000 Canvasbacks on Lake Christina ; the first Can- 

 vasbacks did not reach Delta until ten days later that year. The peak of the 

 Lake Christina population was April 12 and 13, when Smith counted 31,000 

 and 28,500 Canvasbacks respectively. The next day, April 14, when the first 

 of this species reached Delta, the Lake Christina population dropped to 

 12,500. Some Canvasbacks arriving at Delta on the fourteenth no doubt 

 came from Lake Christina. 



The same holds for other ducks; when the time comes to leave Minne- 

 sota waters they fly directly to the Manitoba marshes. Most of the earliest 

 arrivals reach Delta during evening twilight. Ducks are seldom seen through 

 the first mild day of spring; even at sundown none has made its appearance; 



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