Cornfields cut for silage were utilized in fall and winter, but fewer ducks 

 were observed in these fields than in picked cornfields. Feeding ducks were 

 also observed in wheat stubble fields, pastures, and feedlots but less 

 commonly than in the other crop types. 



Movement 



Fall duck concentrations occurred in sections of the river where picked 

 cornfields were available for field-feeding ducks. Secure loafing areas in 

 proximity to water and picked cornfields attracted the largest numbers of 

 dabbling ducks (figure 18). Ducks readily utilized fields for feeding which 

 geese avoided due to poor visibility afforded to birds in the field. Picked 

 cornfields, for example, were avoided by geese except during spring and 

 winter when the hunting season was closed and many of the fields had been 

 used to pasture cattle. Ducks also typically spent less time feeding in 

 fields than did geese, suggesting the need for fields providing a large amount 

 of readily available grain. Ducks commonly loafed on river banks and island 

 edges which afforded less visibility than typical goose loafing areas, indi- 

 cating that geese require more security and are warier than ducks. Ducks 

 would loaf in sections of the river which passed through towns, near farm 

 houses, and under bridges. All of these factors resulted in a more uniform 

 distribution of ducks than of geese within a given section of river. 



Overwintering flocks of ducks between Forsyth and Custer loafed on the 

 ice formed along banks and island margins. In other sections of the river 

 which largely froze over in winter, loafing areas were restricted to pockets 

 where the current was strong enough to keep the water open. Ducks also 

 loafed on open drainage ditches in the valley. Cold weather reduced the 

 number of ducks wintering in the study area (figure 17), but, as long as 

 open water was available and snow in fields was not too deep to hamper feeding 

 efforts, ducks would remain in a given area. Picked cornfields with cobs 

 still handing on stalks provided food for ducks at this time. Ninety-two 

 percent of the observations of ducks field-feeding in winter occurred in 

 cornfields (table 14). 



Banding locations of mallards taken by hunters in counties along the 

 lower Yellowstone are within the limits of mallard migration corridors in the 

 High Plains Unit of the Central Flyway outlined by Bellrose (1968) and shown 

 in figure 19. He described a heavily utilized corridor crossing the Yellowstone 

 River between Billings and Miles City, the existence of which may account for 

 the occurrence between Billings and Miles City of 80 percent of all dabbling 

 ducks observed during aerial censuses. 



Nesting and Brood Rearing 



Although no systematic searches of duck nesting cover were conducted, 

 one blue-winged and one green-winged teal and two mallard nests were 

 encountered during goose-banding operations. Both mallard nests were con- 

 cealed in rose {Rosa sp.) bushes in the interior of large, wooded islands 

 in the Sanders-to-Forsyth section of the river. The teal nests were found 

 in the Myers-to-Hysham section, the green-winged teal nest in dense vegetation 

 under a log near the edge of a large island and the blue-winged teal nest 



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