DABBLING DUCKS 



Data gathered during these duck studies were organized according to six 

 time periods, The wintering period begins when migrations into and out of the 

 area are much reduced and ends with the beginning of the spring migration 

 period when duck numbers increase markedly and when dabbling species other 

 than mallards (pintails {Anas acuta), green-winged teal {Anas oreooa carolinensis ) , 

 baldpates {Anas americana) , for example) appear. The disappearance of migrant 

 flocks and the appearance of breeding ducks (territorial drakes and nesting 

 hens) marks the end of the spring migration period and beginning of the 

 nesting period, which ends when it is believed that most of the clutches have 

 hatched. The brood-rearing period begins at that time and ends when most of 

 the broods can fly and begin to congregate in water areas. The late summer 

 period lasts from then until these groups begin to migrate out of the study 

 area, at which time the fall migration period begins. When most migrant 

 flocks have passed through the study area to southern wintering grounds, the 

 wintering period begins, and the cycle is complete. 



Ducks Present 



Habitat utilization and population levels of dabbling ducks in the lower 

 Yellowstone River Valley change markedly through the year. Dabbling duck 

 numbers observed during aerial censuses along the river between Billings 

 and Fairview are indicative of these changes (figure 17). Numbers of dabbling 

 ducks were highest during the spring and fall migration periods and lowest 

 during the brood-rearing and late summer periods. 



Mallards {Anas platyrhynchos ) were the most common species of dabbling 

 duck present in the study area at all times of the year, although the percentage 

 of mallards was highest whenever field-feeding flocks of ducks were present. 

 Pintails also occurred in large field-feeding flocks but only for short 

 periods during spring migration. 



The first spring migrant dabbling ducks, observed in early March both 

 years of the study, were pintails, blue-winged teal {Anas discors), green- 

 winged teal, and baldpates. Numbers of these species increased while flocks 

 of gadwalls {Anas strep era ) , northern shovel ers {Anas clypeata) , and wood 

 ducks {Aix sponsa) began to occur in the study area. Diving ducks, including 

 redheads {Aythya americana) , canvasbacks {Aythya valisineria) , ring-necked 

 ducks {Aythya collaris), and lesser scaup {Aythya af finis) , were also observed 

 as spring migrants, as were ruddy ducks {Oxyura jamaieensis ) (appendix F). Only 

 the dabbling ducks were seen throughout the spring and into the summer, 

 nesting along the river and in stockponds near the river. 



Crops and Forage Utilized 



Dabbling ducks were observed feeding and/or loafing in fields throughout 

 the year. Picked cornfields were the most heavily utilized, based on observa- 

 tions recorded throughout the entire study period (table 14). From spring 

 migration through late fall, observations of ducks in barley stubble fields 

 also accounted for a high percentage of the field-feeding observations. 



47 



