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).
| 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. |
||||||||
Previous Section -- Components of Mallard Production
Return to Contents
Next Section -- Discussion
