Flocks of spring migrants divide into smaller units on approaching the marsh. 



These April flocks leaving Delta are smaller than the migrant bands of 

 October, although, as in autumn, it is usual to see several, often many 

 groups traveling across the sky at the same moment. Sowls (1951:34) found 

 twelve to be the average for migrating Pintail flocks, and I have never seen 

 a departing flock of more than twenty birds. The small clusters usually are 

 made up of birds of one species, although in Mallard and Pintail it is not 

 uncommon to see both kinds together. Most of the river ducks are paired, 

 each hen leading her drake, which follows so closely that the pair rather 

 than the individual makes up the unit of a flock. Some Canvasbacks and 

 other diving ducks are in groups of twos, but many bands boast only one 

 female, probably not yet mated, the several male companions undoubtedly 

 her suitors. 



These small companies leaving Delta must join to make larger flocks once 

 the journey is under way, for on the wheat prairie south of the marsh I have 



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