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Response of Nesting Ducks to Predator Exclosures and Water Conditions During Drought

Tables

Table 1. Area of cover types (ha) on study areas in North Dakota (Kulm, Jamestown) and Minnesota (Detroit Lakes), 1991.
  Study area
Cover typea Kulm Jamestown Detroit Lakes
Barren 20.5 21.4 31.5
Cropland 1,673.1 2,761.5 3,140.8
CRP cover 86.8 1040.6 42.5
Grassland 1,710.3 207.9 228.5
Grassland - fencedb 0.8 0.0 0.1
Grassland - wildlifec 66.3 39.4 40.7
Hayland 235.9 25.7 154.8
Other 148.8 157.8 268.3
Planted cover 76.1 34.0 64.9
Planted cover - fencedb 22.3 27.2 23.3
Right-of-way 86.0 105.4 62.9
Permanenet wetland 17.3 1.2 450.9
Semipermanent wetland 561.5 338.7 272.2
Seasonal wetland 274.5 200.4 109.7
Temporary wetland 97.1 114.3 53.1
Fencedb wetland 0.5 0.0 1.4
Woodland and shrubland 0.0 2.5 132.5
Total 5,077.9 5,077.9 5,077.9
aCowardin et al. (1988b) presented detailed descriptions of the upland cover types and basin classes.
b"Fenced" covers are inside predator exclosures.
cGrassland managed by the U. S. Fish and Wildlife Service.

 

Table 2. Results of regression analyses relating numbers of breeding pairs of 5 species of ducks to areas or numbers of ponds for 3 study areas and 5 years in North Dakota and Minnesota. R2* is the proportion of variation attributable to β1xij (β1ixij for blue-winged teal and area of ponds) in the regression model where pairs = β0i + β1xij.(β0i + β1ixij for blue-winged teal and area of ponds). Subscript i distinguishes study areas and subscript j distinguishes years.
  H0:β11 = β12 = β13 = β1a H0: β1 = 0| β11 = β12 = β13 = β1b  
  Area of ponds Number of ponds Area of ponds Number of ponds R2*
Species F2,9 P F2,9 P F1,11 P F1,11 P Area of ponds Number of ponds
Mallard 0.27 0.7671 0.01 0.992 17.73 0.0015 8.48 0.0141 0.359 0.253
Gadwall 0.23 0.8009 0.05 0.948 3.76 0.0784 0.94 0.3533 0.109 0.034
Blue-winged teal 8.48 0.0085 1.55 0.263   12.84 0.0043 0.743 0.425
Northern shoveler 1.11 0.3699 0.56 0.592 11.78 0.0056 13.36 0.0038 0.349 0.371
Northern pintail 1.37 0.3016 0.66 0.540 32.79 0.0001 22.73 0.0006 0.457 0.412
aSlopes are equal for all areas.
bSlope equals zero, conditional on the same slope for all areas.

 

Table 3. Number of nests of 5 duck species found inside predator exclosures on study areas in North Dakota (Kulm, Jamestown) and Minnesota (Detroit Lakes), 1987-91.
    Nests in exclosure
Study Area Species 1987 1988 1989 1990 1991 All years
Kulm Mallard 10 9 16 5 7 47
Gadwall 10 10 23 10 12 65
Blue-winged teal 1 0 3 0 1 5
Northern shoveler 2 1 3 0 0 6
Northern pintail 1 1 4 2 1 9
All species 24 21 49 17 21 132
Jamestown Mallard 2 15 12 7 6 42
Gadwall 14 22 41 41 33 151
Blue-winged teal 12 2 1 3 1 19
Northern shoveler 0 2 3 4 4 13
Northern pintail 5 3 0 2 1 11
All species 33 44 57 57 45 236
Detroit Lakes Mallard 0 5 10 10 11 36
Gadwall 0 0 1 1 1 3
Blue-winged teal 2 4 6 20 10 42
Northern shoveler 0 0 0 1 0 1
Northern pintail 0 0 0 2 0 2
All species 2 9 17 34 22 84
All areas   59 74 123 108 88 452

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