Waterfowl use of tall, relatively homogeneous upland nesting cover established as part of the North American Waterfowl Management Plan has often been lower than predicted by computer planning tools. Little information exists regarding the influence of patchiness or the spatial scales at which mallards (' Areas platyrhynchos') select nesting habitats. The present study addresses these ques ions at the level of the nest site, and provides new information to managers concerned with improving the productivity of nesting habitat for prairie waterfowl. Data were collected in conjunction with Prairie Habitat Joint Venture Assessment research, near Minnedosa, Manitoba in 1998. A random sample of 64 mallard nests were chosen from all nests located on a 65 km2 study area. Vegetation characteristics were measured within 4 x 4, 16 x 16, and 32 x 32 meter sample grids centered at each nest and at paired non-nest points. Observed habitat preferences suggest that management for nesting cover with an intermediate height and density, a high diversity and interspersion of grasses, forbs and shrubs, and fine scale structural heterogeneity may increase its attractiveness to nesting mallards. (Abstract shortened by UMI.)