Northern Prairie Wildlife Research Center
Mallard and gadwall nest densities were highest in those cover types with the highest visual obstruction ratings. Cover preference in descending order of use was seeded nesting cover, odd areas, roadside, dry wetland, and canal-side. Blue-winged teal nest densities were highest in dry wetland and roadside. Nesting success was different among years, but not among cover types. There was no population increase at any cover type due to homing hens. Overall nesting success was 11, 10, and 23% for mallards, gadwalls, and blue-winged teal, respectively. Recruitment of fledged young was similar for yearling and adult mallard females. Production from yearling gadwall hens was a meager 0.2 young fledged/female. Clutch size was not different between yearling and adult mallard and blue-winged teal hens, but clutch size for all 3 species declined as the nesting season advanced.
More ≥1-year-mallard hens and ≥2-year-old gadwall hens that nested successfully 1 year returned to the study areas the following year than did unsuccessful hens. Gadwall hen return rates also increased with age. Blue-winged teal hen return rates averaged 4% and were not related to hen success or hen age. Mallard and gadwall hens that nested successfully 1 year used the same cover type the next year, Successful returning mallard hens also nested closer to the previous nest site than unsuccessful hens, Twenty-nine percent of hatching year (HY) mallard females returned to the study area, and all of these returned as yearlings (second summer). Nine percent of HY gadwalls returned, approximately half as yearlings and the remainder as 2 year olds.
Duckling survival from hatching until near fledging was 0.681 for mallards and 0.828 for gadwalls. An overall direct band recovery rate of 8% for HY mallard hens was not different than that of older hens. Gadwall direct band recovery rates decreased through the HY (11%), yearling (5%), and >2-year (1%) age classes.