Factors Associated with Duck Nest Success
in the Prairie Pothole Region of Canada
Daily Rate of Nest Predation
Predation rates on nests of the 5 common species tended to decrease as the breeding season progressed (Fig. 3). The trend was consistent among species, but significant only for the northern shoveler (X2 = 3.85, 1 df, P = 0.05). The decline in predation rates was not consistent among area-years. We detected significant interactions between area-year and search period for all species (mallard, X2 = 121.2, 56 df, P < 0.01; gadwall, X2 = 39.4, 20 df, P < 0.01; northern shoveler, X2 = 40.0, 26 df, P = 0.03; northern pintail, X2 = 104.9, 40 df, P < 0.01) except blue-winged teal (X2 = 29.7, 23 df, P = 0.13). We could not explain interactions by examining annual wetness measurements. Interactions between area-year and search period were still significant for 8 of 15 categories (5 species, 3 wetness intervals) and for at least 1 species in each wetness interval. Where we did not detect interactions and where differences in nest predation rates among search periods were significant, rates were lower in later search periods.
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