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

Fates of Unsuccessful Nests

We estimated that predators destroyed 65-72% of the nests of the 5 common species (Table 11). An additional 5-6% likely failed because predators caused females to abandon nests; these nests contained >=1 depredated egg. Pooled percentages of nests in these 2 categories indicated that 77-78% of mallard, gadwall, blue-winged teal, and northern shoveler nests and 71% of northern pintail nests failed to hatch because of predation.

We estimated that agricultural operations, mostly tillage, destroyed 17% of northern pintail nests and 2-3% of those of the other 5 common species. Nests in Cropland usually were dispersed widely, so individual tillage operations seldom destroyed many nests. However, in 1983 we found an unusually high concentration of nests (0.18/ha) in 5 fields of standing stubble on the Hay Lakes and Holden study areas during the first 2 weeks of May. The nests (46 northern pintails, 11 mallards, and 3 northern shovelers) were in 340 ha of wheat that had been cut and swathed the previous autumn, but not harvested because of deep snow; most nests were under swaths and only 5 (8%) hatched. In contrast, we found only 0.01 nest/ha (93 northern pintails, 53 mallards, 12 northern shovelers, 9 blue-winged teals, and 2 gadwalls) in all the remaining stubble fields (15,174 ha) searched during the study; 48 (28%) of these nests hatched.

We estimated that weather events destroyed 1% of nests overall. Snowstorms mainly affected early-nesting mallards and northern pintails when eggs were chilled or nests were abandoned after being buried in deep snow. Among nests known to be present on the Tichfield Study Area in 1982 during the storm of 26-29 May, 14 of 16 (88%) failed because all embryos died or nests were abandoned (10 of 11 mallards and 4 of 5 northern pintails); 8 of the 16 nests were within 4 days of hatching. Among nests known to be present on the Goodwater Study Area in 1983 during the storm of 8-14 May, 16 of 77 (21%) failed as a result of the storm (9 of 43 northern pintails, 6 of 32 mallards, 1 of 1 northern shoveler, and O of 1 American wigeon).

Flooding from heavy rain resulted in abandonment of numerous duck nests located near or in wetlands and drainage ditches on Hay Lakes and Holden study areas in 1983. Among nests known to be present on those study areas during the storms of 18-30 June, 101 of 254 (40%) were abandoned or washed away because of flooding (27 of 61 mallards, 16 of 45 blue-winged teals, 16 of 34 lesser scaups, 19 of 22 ruddy ducks, 8 of 31 northern shovelers, 7 of 21 redheads, 1 of 9 gadwalls, 2 of 7 northern pintails, 1 of 7 canvasbacks, 1 of 5 green-winged teals, 1 of 1 cinnamon teal, and O of 7 American wigeons).

We found 190 nests (all species and area-years pooled) that were abandoned without evidence of egg destruction. We found dead females or their remains at 11% of these nests, but no probable cause for abandonment at the remaining.

Table 11. Average estimated percentage of nests by fate and causes of failure among unsuccessful nests of the 5 common species of dabbling ducks in the Prairie Pothole Region of Canada, 1982-85. Percentages are unweighted averages of all area-yearsa. Number of area-years vary because estimates of nest success were not available for some species in some years. Rows sum to 100% with rounding errors.
Species Area-years Successful (%) Unsuccessful (%)
Destroyed Abandoned
Predation Farm equipment Other Predation Weather Other
Mallard 31 11 72 3 <1 6 2 6
Gadwall 29 14 72 2 <1 6 1 5
Blue- winged teal 30 15 72 2 <1 5 1 6
Northern shoveler 29 12 72 2 <1 6 1 7
Northern pintail 30 7 65 17 <1 6 1 4
aArea-year refers to 1 area studied for 1 year.

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