Waterfowl Production on the Woodworth Station
in South-central North Dakota, 1965-1981

Table 41. Reduction of brood size of 12 duck species between age classes,
Woodworth Study Area, 1965-81.


Table 41. Reduction of brood size of 12 duck species between age classes, Woodworth Study Area, 1965-81.
      Brood size reduction between average successful clutch size and average total brood size Brood size reduction between average successful clutch size and average Class Ib brood size Brood size reduction between Class Ib brood and average total brood size
Species Average successful clutch size 17-year average brood size Number Percent Number Percent Number Percent
Dabbling ducks
Mallard 9.2 5.8 3.4 37 2.3 25 1.1 16
Gadwall 9.7 7.2 2.5 26 1.9 20 0.6 8
American wigeon 8.6 6.6 2.0 23 1.8 21 0.2 3
Green-winged teal 8.8 5.4 3.4 39 2.8 32 0.6 10
Blue-winged teal 10.2 6.7 3.5 34 3.4 33 0.1 1
Northern shoveler 9.9 5.6 4.3 43 3.5 35 0.8 13
Northern pintail 7.8 4.4 3.4 44 0.3 4 3.1 41
Total dabbling ducks 9.8 6.6 3.2 33 2.7 28 0.5 7
Diving ducks
Redhead 10.0a 6.2 3.8 38 3.3 33 0.5 7
Canvasback 7.7a 4.7 3.0 39 2.3 30 0.7 13
Lesser scaup 9.9 7.5 2.4 24 3.1 31 1.3d 19d
Ring-necked duck 9.2b 6.8 2.4 26 5.2 57 2.8d 70d
Ruddy duck 6.6a 4.7 1.9 29 1.9 29 0.0 0
Total diving ducks 8.7c 5.6 3.1 36 3.1 36 0.0 0
Total broods 9.0c 6.4 2.6 29 2.2 24 0.4 4
aBased on data by Stoudt (1971).
bBased on data by Smith (1971).
cMean of means for species in these groups.
dThese were increases in brood sizes and not attrition.


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