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Determinants of Breeding Distributions of Ducks

Results


Dynamics of the Wetland Habitat

Average pond densities varied widely among the strata. Highest densities were observed in southwestern Manitoba and southeastern Saskatchewan and lowest densities along the eastern and western edges of the Dakotas and in Montana (Fig. 2).


gif -- Prairie Pothole Region quartiles

Figure 2. Pond density by stratum, 1955-81.

Variation among years in pond counts was expected, as the prairie and parkland area is well known for recurring droughts and intervening wet periods. LS means were lower than ordinary means, especially in the first few years (Fig. 3). Surveys were begun during a very wet period; pond densities never again reached the numbers attained in 1955. After a decline from 1955 to 1959, densities of ponds have oscillated around a mean of about 4/km2 (10/sq mile).

gif -- Graph Pond Density by Year

Figure 3. Pond density (ponds/km2) by year.

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