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Factors Associated with Duck Nest Success
in the Prairie Pothole Region of Canada

Geographic and Temporal Effects on Mallard Production

We detected a significant interaction between year and study area for temporary wetlands and seasonal wetlands among pooled results from areas studied in 1983 and 1984 or 1984 and 1985 (Table 16), indicating that drought did not affect each study area similarly in all years. Temporary wetlands were highly variable (both geographically and annually), seasonal wetlands were less variable than temporary ones, and semipermanent wetlands were even less variable. Temporary wetlands were about equally variable from year to year as among areas, as indicated by the ratios of their CV's (CVY/CVSA = 0.91). Seasonal wetlands were more variable year to year than among areas (CVY/CVSA = 1.49). As expected from their greater permanence, semipermanent wetlands varied less from year to year than among areas (CVY/CVSA = 0.49).

Pairs were moderately variable, and equally so among years and areas (CVY/CVSA = 0.95). Nest success also was moderately variable, but somewhat more so among years than areas (CVY/CVSA = 1.69).

Table 16. Statistics associated with variance components of factors involved in mallard production: mean, variance components, and coefficients of variation (CV = square root of variance component divided by mean).
Dependent variable Mean Variance component CV (%)
Error Study area Year Study area times year Error Study area Year
Temporary wetlandsa 7.97 22.39 51.55 43.37 46.11 59 90 82
Seasonal wetlandsa 19.39 156.73 83.21 184.81 175.31 64 47 70
Semipermanent wetlandsa 16.01 86.83 46.98 11.04 0b 58 43 21
Mallard pairs 62.58 611.93 547.87 470.74 0b 40 37 35
Nest success rate 0.1034 0.0047 0.0007 0.0021 0b 81 26 44
aWetlands refer to those that contained visible standing water in May.
bVariance component not significantly different from zero.
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