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

Nest Success and Percentage Cropland


We detected an overall effect of the percentage of Cropland present on study areas on nest success of the 5 common species (mallard– F = 12.7; 2, 13 df; P < 0.01; gadwall– F = 8.9; 2, 12 df; P < 0.01; blue-winged teal– F = 8.8; 2, 13 df; P < 0.01; northern shoveler– F = 5.2; 2, 13 df; P = 0.02; northern pintail– F = 19.0; 2, 13 df; P < 0.01). Nest success was negatively related to the percentage of Cropland present on study areas in parkland and prairie (Table 12). On study areas in parkland, we predicted nest success would be at the threshold level for population stability for northern pintails when Cropland composed 6% of the habitat present (P = 0.03); results for other species in parkland were not significant (P > 0.15). We rejected the estimate for northern pintails because the predicted value was outside the range of Cropland availability that we observed (Table 2). In prairie, however, we predicted nest success would be at threshold levels for population stability for all of the 5 common species when Cropland composed 46-63% of the habitat present. Interpretation of regression slopes indicated that on average in prairie, nest success was at threshold levels when Cropland composed 56% of the habitat present and that nest success decreased about 4 percentage points for every 10 percentage points increase in Cropland.

Table 12. Summary of regressions of average estimates of nest success on percentage of Croplanda available on individual study areas in parkland (P) and Prairie (G) of Prairie Pothole Region of Canada of the 5 common duck species, 1982-85, and predictions of mean percent of Cropland above which nest success is below threshold levelb thought necessary for population stability.
Species Physio- graphic zone Slope SE tc P Threshold Predicted mean % cropland SE
Mallard P -0.119 0.090 -1.32 0.21 15 ncd -
G -0.448 0.092 -4.86 <0.01* 63 11.20
Gadwall P -0.083 0.131 -0.63e 0.54 20 nc -
G -0.538 0.129 -4.17e <0.01* 59 13.06
Blue-winged teal P -0.185 0.120 -1.54 0.15 20 nc -
G -0.484 0.124 -3.90 <0.01* 61 13.87
Northern shoveler P -0.086 0.101 -0.85 0.41 20 nc -
G -0.342 0.110 -3.11 <0.01* 50 16.50
Northern pintail P -0.142 0.058 -2.45 0.03* 15 6 26.12
G -0.326 0.058 -5.65 <0.01* 46 10.15
aBased on Table 2.
bFrom Cowardin et al. (1985) and Klett et al. (1988).
ct statistic for testing of slope is equal to zero, 13 df.
dNot calculated because regression slope not significantly different from zero (P> 0.05).
e12 df.
*Denotes significance (P <0.05).

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