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Effects of Weather on Breeding Ducks in North Dakota

Breeding Pair Populations

Counts of breeding pairs are available for Salyer during 1949-63 and for Woodworth during 1965-77 (Table 3). All species varied in number from year to year. Coefficients of variation for the four species averaged 36% at Salyer and 41% at Woodworth; numbers of redheads were particularly variable at Woodworth.

The four species tended to vary together from year to year. Numbers of mallards, gadwalls, and blue-winged teal at Salyer averaged higher in 1956-63 than in 1949-55; redheads did not exhibit this trend. All species at Woodworth were more abundant during years of good wetland conditions and less abundant when many ponds were dry.

Species Composition (%) of these four species was different at the two study areas:


Mallard Gadwall Blue-winged teal Redhead
Salyer 19.0 23.5 47.1 10.4
Woodworth 14.7 19.0 62.4 4.0

Woodworth had proportionately more blue-winged teal and fewer redheads than Salyer.

Table 3. Summary statistics of abundance of four duck species at the Salyer (S) and Woodworth (W) study areas. Brood to pair ratios are ×1,000 for Salyer and ×100 for Woodworth.
Abundance Species and study area
Mallard Gadwall Blue-winged teal Redhead
S W S W S W S W
Breeding population (na) 15 13 15 13 15 13 15 13
Mean 1,022 54 1,263 70 2,533 229 559 14
SDb 329 13 534 17 745 86 218 11
CVc(%) 32 24 42 24 29 38 39 79
Broods (n) 14 13 14 13 14 13 14 13
Mean 9.9 12.8 66.9 22.9 72.9 84.7 19.9 3.4
SD 8.0 8.0 51.3 10.5 85.6 48.0 17.2 2.6
Ratio (n) 14 13 14 13 14 13 14 -
Mean 10.3 27.1 65.3 36.0 31.9 39.4 38.5 -
SD 7.4 19.4 72.0 21.3 43.2 21.0 35.8 -
an=number of years.
bSD=standard deviation.
cCV=coefficient of variation.
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