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Our North Dakota reference area is part of the Prairie Pothole Region of central North America, which includes the aspen parkland transition area to the north. Although the Prairie Pothole Region is a relatively small part (12%) of the North American mallard breeding range (Fig.9), it is the nesting ground for about half of the continental mallards (Pospahala et al. 1974). Because of the large number of mallards nesting in the Prairie Pothole Region, factors that significantly affect mallards there are of consequence to the continental population.

The Prairie Pothole Region was settled by Europeans during the past 100 years; since settlement began there have been considerable changes in mallard habitats, human interactions with mallards, and predator compositions and densities. Our purpose in Part Three is to examine the changes in our North Dakota reference area since pristine times that relate to mallard sex ratios and to place them in perspective relative to the entire Prairie Pothole Region. Emphasis is on factors affecting densities and distributions of mallards and of canids. Finally, we conclude by employing the predictive model of Part Two to reconstruct probable mallard sex ratios during pristine times in that region.