USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

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

Mortality of Adult Ducks


We found remains of 573 dead, adult ducks on study areas during 1983-85 (Table 13). Remains were from red fox dens (20%), duck nests (13%), raptor nests (4%), roadsides (2%), and other locations (61%). We found no duck remains at coyote dens. Raptor nests with remains were those of great horned owl, red-tailed hawk, and Swainson's hawk; >95% of remains at raptor nests were on the ground.

Table 13. Number of adult ducks from current year found dead during 1 May-5 July on all study areas in the Prairie Pothole Region of Canada by year and percentages by type of location where found. Columns sum to 100% with rounding errors.
1983 1984 1985 Total
All species Mallard
Number of ducks 185 128 260 573 240
Locations (%)
Red fox dens 17 20 22 20 18
Duck nests 13 8 15 13 6
Raptor nests 1 15 1 4 3
Roadsides 3 2 <1 2 <1
Other locations 66 55 61 61 73

Remains were of 7 dabbling duck and 6 diving duck species (Table 14). Dabbling ducks represented a greater proportion (94%) and diving ducks a lesser proportion (6%) of remains than expected from their proportions in the breeding population (X2 = 103.65, 1 df, P < 0.01). We report only data for all years combined because annual comparisons of species found dead with those in the breeding population were nearly identical. We detected differences in proportions of individual species found dead among dabbling ducks, relative to their occurrence in breeding populations (X2 = 118.94, 6 df, P < 0.01), but not among diving ducks (X2 = 4.36, 4 df, P = 0.36). There were nearly one-third more dead mallards and nearly twice as many dead northern pintails as expected from their relative abundance in the breeding population. Conversely, American wigeons, blue-winged teals, and northern shovelers were less abundant among dead ducks than expected.

Table 14. Numbersa and proportions of ducks in breeding population and of adult ducks found dead for all study areas and years combined in the Prairie Pothole Region of Canada, 1983-85.
Species Breeding population Dead ducks
No. counted Proportion of dabblers or divers No. found Proportion Proportion found dead
95% CL Significanceb
Mallard 7,136 0.316 240 0.467 0.424-0.510 >
Gadwall 2,167 0.096 40 0.078 0.055-0.101 ns
American wigeon 1,545 0.068 21 0.041 0.024-0.058 <
Green-winged teal 533 0.024 7 0.014 0.004-0.024 ns
Blue-winged teal 5,540 0.245 64 0.125 0.096-0.153 <
Northern shoveler 2,892 0.128 36 0.070 0.048-0.092 <
Northern pintail 2,801 0. 124 106 0.206 0.171-0.241 >
Total dabblers 22,614 1.001 514 1.001
Redhead 1,290 0.182 3 0.115 0.000-0.238 nt
Canvasback 942 0.133 6 0.231 0.069-0.393 nt
Lesser scaup 3,338 0.470 14 0.538 0.347-0.730 nt
Bufflehead 241 0.034 1 0.038 0.000-0.112 nt
Ruddy duck 1,290 0.182 2 0.077 0.000-0.179 nt
Total divers 7,101 1.001 26 0.999
Dabblers 22,614 0.761 540c 0.942 0.923-0.961 >
Divers 7,101 0.239 33d 0.056 0.039-0.077 <
Total ducks 29,715 1.000 573 0.998
aSummed across 1983, 1984, and 1985.
bNotation implies that proportion of the dead ducks for an individual species is significantly greater than (>), significantly   less than (<), or not significantly different from (ns) the proportion of that species in the breeding population, or that no   test was conducted (nt) because overall chi-squared test was not significant. Significance level used was P <0.05.
cIncludes ducks identified to dabbler, but not to species.
dIncludes ducks identified to diver, but not to species.

We determined sex of 501 dead ducks (Table 15). More females than males were tallied each year among all species of dabbling ducks, except for mallards in 1984, gadwalls in 1985, and a few species for which samples were small. Disparities in the expected 50:50 ratio of females to males were significant in mallards (X2 = 20.25, 3 df, P < 0.01) and northern shovelers (X2 = 8.07, 2 df, P = 0.02), but not in gadwalls (X2 = 0.82, 2 df, P = 0.66), blue-winged teals (X2 = 4.52, 2 df, P = 0.10), or northern pintails (X2 = 5.33, 3 df, P = 0.15). Among mallards, significantly more females than males were found dead in 1983 (X2 = 14.63, 1 df, P < 0.01) and 1985 (X2 = 5.63, 1 df, P = 0.02), but not in 1984 (X2 = 0.0, 1 df, P = 1.00). Among northern shovelers, significantly more females than males were found dead in 1983 (X2 = 6.40, 1 df, P = 0.01), but not in 1985 (X2 = 1.67, 1 df, P = 0.20); only 10 northern shovelers were found dead in 1984.

Table 15. Number of ducks found dead, number identified to sex, and percentage of females among those identified to sex for all study areas combined by year in the Prairie Pothole Region of Canada.
Species 1983 1984 1985 Total
No. found Sex known % female No. found Sex known % female No. found Sex known % female No. found Sex known % female
Mallard 78 70 72.9 69 62 50.0 93 86 62.8 240 218 62.4
Gadwall 11 11 63.6 6 6 100.0 23 22 50.0 40 39 61.5
American wigeon 14 11 63.6 2 1 100.0 5 5 80.0 21 17 70.6
Green-winged teal 2 2 50.0 1 1 0.0 4 4 75.0 7 7 57.1
Blue-winged teal 16 15 73.3 6 6 83.3 42 39 59.0 64 60 65.0
Northern shoveler 14 10 90.0 6 4 75.0 16 15 66.7 36 29 75.9
Northern pintail 40 37 59.5 20 19 63.2 46 45 62.2 106 101 61.4
Unknown dabbler 5 1 0.0 10 1 100.0 11 4 100.0 26 6 83.3
Total dabblers 180 157 68.8 120 100 59.0 240 220 62.3 540 477 63.7
Redhead 0 - - 0 - - 3 3 67.7 3 3 66.7
Canvasback 1 1 0.0 0 - - 5 5 60.0 6 6 50.0
Lesser scaup 3 3 33.3 5 4 50.0 6 4 75.0 14 11 54.6
Bufflehead 0 - - 1 1 0.0 0 - - 1 1 0.0
Ruddy duck 1 1 0.0 1 1 100.0 0 - - 2 2 50.0
Unknown diver 0 - - 1 0 - 6 1 100.0 7 1 100.0
Total divers 5 5 20.0 8 6 50.0 20 13 69.2 33 24 54.2
Total ducks 185 162 67.3 128 106 58.5 260 233 62.7 573 501 63.3

Cause of mortality seldom could be determined because dead ducks were represented mostly by scattered feathers or feathered body parts, but predators were strongly implicated. Nearly all dead ducks had been fed on by predators, and nearly all fresh carcasses that we examined had predator-inflicted wounds with recent hemorrhaging; all dead females found at nests showed evidence of predation. No other causes of mortality were indicated except for a few (n = 11) collisions with vehicles or overhead wires. We observed 22 instances of raptors killing ducks or feeding on fresh duck carcasses—10 by Swainson's hawks, 9 by northern harriers and 1 each by a ferruginous hawk, falcon (species unknown), and great horned owl.

The incidence of dead female mallards in relation to size of breeding populations on individual study areas provided insight into the extent of mortality that occurred. We found an average of 0.27, 0.14, and 0.22 dead mallard females/km² on all study areas during 1983-85, respectively. Based on annual breeding population estimates of 8.3, 3.7, and 3.2 mallard females/km² (Table 1 of Appendix A), we estimated that 3.3, 3.7, and 6.9% of available female mallards were found dead during 1983-85, respectively.


Previous Section -- Nest Success and Percentage Cropland
Return to Contents
Next Section -- Components of Mallard Production

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/birds/nestsucc/mortalad.htm
Page Contact Information: Webmaster
Page Last Modified: Friday, 01-Feb-2013 19:39:57 EST
Sioux Falls, SD [sdww55]