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Northern Prairie Wildlife Research Center

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Nesting Waterfowl and Water Birds on Natural Islands in the Dakotas and Montana

Tables


Table 1.  A comparison of the species composition of breeding waterfowl counted in North and South Dakota wetlands in May 1985 and 1986, with the species composition of waterfowl nests on islands in the prairie pothole region of North Dakota and South Dakota, 1985 and 1986.
Species Species composition (%)
Dakota breeding population Island nesting population Use index a
Mallard
15.2 32.4 2.13
Gadwall
8.6 41.6 4.84
American wigeon
5.5 0.3 0.05
Green-winged teal
2.1 0.2 0.10
Blue-winged teal
32.7 6.2 0.19
Northern Shoveler
10.7 0.8 0.07
Northern pintail
9.2 4.4 0.48
Redhead
5.1 2.3 0.45
Lesser scaup
3.5 6.8 1.94
Ruddy duck
5.8 0.1 0.02
Canada goose
0.1 4.8 48.00
a Use index was calculated by dividing percentage of island nesting population by percentage of Dakota breeding population.

 

Table 2.  Apparent nest success (%) for 11 waterfowl species nesting on islands with and without predator control in the prairie pothole region of North Dakota, South Dakota, and northeastern Montana, 1985 and 1986.
Species No predator control Predator control P a
n islands n nests % success n islands n nests % success
Mallard 80 320 58 19 454 76 0.01
Gadwall 73 373 58 16 621 80 <0.01
American wigeon 1 1 100 3 7 55 b
Green-winged teal 0 0   4 5 39 b
Blue-winged teal 59 110 52 14 39 68 0.20
Northern shoveler 13 15 88 4 4 100 0.44
Northern pintail 35 78 77 11 27 72 0.63
Redhead 21 53 51 1 1 100 b
Lesser scaup 44 141 66 7 22 57 0.55
Ruddy duck 3 3 67 0 0   b
Total or Mean of x 140 1,094 57 20 1,180 76 <0.01
Canada Goose 50 94 81 5 21 70 0.47
Grand Total or Mean of x 148 1,188 60 20 1,201 76 <0.01
a Probability values from ANOVA of nest success between islands with and without predator control.
b Insufficient data for ANOVA.

 

Table 3.  Logistic regression models relating presence or absence of a species to island habitat features for 5 duck species and American avocets nesting on islands in North Dakota, South Dakota, and Montana, 1985 and 1986.
Variable 1985 1986
Coef. SE P Coef. SE P
Mallard
Wetland salinity a 0.13 0.07 0.07 NS b    
Tall shrub −0.16 0.06 <0.01 NS    
Distance to shore NS     NS    
Wetland Class V NS     NS    
Wetlands <1.6 km 0.05 0.02 0.01 NS    
VOR 0.65 0.25 0.01 0.49 0.14 <0.01
Low shrub NS     NS    
Bare NS     NS    
Island size NS     NS    
Gadwall
Wetland salinity a 0.17 0.07 0.02 0.29 0.08 <0.01
Tall shrub −0.20 0.10 0.04 −0.35 0.13 0.01
Distance to shore 0.01 <0.01 0.08 0.01 <0.01 0.01
Wetland Class V NS     NS    
Wetlands <1.6 km 0.03 0.01 0.01 NS    
VOR NS     NS    
Low shrub 0.03 0.02 0.05 0.03 0.01 0.01
Bare NS     −0.03 0.01 0.02
Island size NS     NS    
Blue-winged teal
Wetland salinity a 0.18 0.07 0.01 NS b    
Tall shrub −0.18 0.07 0.01 NS    
Distance to shore 0.01 <0.01 0.08 0.01 <0.01 0.09
Wetland Class V NS     1.43 0.57 0.01
Wetlands <1.6 km 0.03 0.01 0.01 NS    
VOR NS     0.55 0.17 <0.01
Low shrub NS     NS    
Bare −0.09 0.05 0.07 NS    
Island size NS     0.24 0.13 0.07
Northern pintail
Wetland salinity a NS     0.32 0.08 <0.01
Tall shrub NS     −0.53 0.24 0.03
Distance to shore NS     NS    
Wetland Class V NS     1.13 0.58 0.05
Wetlands <1.6 km 0.02 0.01 0.07 NS    
VOR NS     NS    
Low shrub 0.03 0.01 0.08 NS    
Bare NS     −0.03 0.02 0.08
Island size NS     0.27 0.12 0.03
Lesser scaup
Wetland salinity a 0.23 0.10 0.02 0.12 0.05 0.01
Tall shrub NS     NS NS  
Distance to shore NS     NS    
Wetland Class V 2.69 1.19 0.02 1.42 0.54 0.01
Wetlands <1.6 km NS     NS    
VOR −1.19 0.47 0.01 NS    
Low shrub NS     NS    
Bare NS     NS    
Island size NS     NS    
American avocet
Wetland salinity a NS     0.14 0.05 <0.01
Tall shrub NS     NS    
Distance to shore NS     NS    
Wetland Class V NS     NS    
Wetlands <1.6 km NS     NS    
VOR NS     NS    
Low shrub NS     NS    
Bare 0.08 0.03 0.01 0.04 0.01 <0.01
Island size NS     NS    
a Logistic regression coefficients and standard errors (SE) are expressed as micromhos/cm³ × 10³.
b NS = Not significant.