Fig. 3. Mean nest success of dabbling ducks as a function of proportion cropland and pond density in the Pothole Prairie Region of Canada and the United States, 1964–1995. Nest success estimates were collected from published and unpublished studies. Agricultural data are from the Census of Agriculture collated by Miller (2000) and represent the proportion of strata from aerial waterfowl surveys (Smith 1995) covered in row crops. Lines indicate the model-averaged predicted values from 12 general linear mixed models depicting possible relationships between nest success, country, proportion cropland, and pond density. Note differences in the x-axes between countries with respect to pond density.