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Aerial view of cultivated cropland—area managed for duck nesting shown in upper right.

Topography was gently rolling, and climate was continental. Cropland comprised 75% of the landscape and was used primarily for small-grain production, especially wheat, but also corn and sunflowers. Grassland (pastures, hayfields, uplands associated with 2 federally managed Waterfowl Production Areas, and narrow strips around cropland fields, wetlands, and along roads) comprised 15% of the landscape. Wetland comprised 9% of the landscape, including 6 large (124- to 865-ha) semipermanent or seasonal basin wetlands and numerous small temporary wetlands (classification according to Stewart and Kantrud [1971]). Woodland, primarily trees in scattered farmsteads and windbreak plantings, comprised <1% of the landscape. Annually, small-grain stubble fields comprised about 24% of the cropland before cultivation in spring. Row-crop (corn and sunflower) stubble fields comprised <1% of cropland in the spring of 1976 and 1977, but increased to 4% in 1978, primarily due to increased planting of sunflowers.

During the study, April-July mean temperatures were above the long-term mean of 14.0° C (+2.0° in 1976, +3.6° in 1977, +1.3° in 1978) and April-July mean precipitation was at or below the long-term mean of 7.0 cm (–2.7 cm in 1976, +0.02 cm in 1977, –0.6 cm in 1978) (National Oceanic and Atmospheric Administration 1976, 1977, 1978). Wetlands began to draw down in 1976, to the extent that only the deepest basins retained water by mid-June of that year (Greenwood 1981). Wetland conditions were similar in 1977, but improved in 1978 due to runoff from snow melt. Fritzell (1978) and Greenwood (1981) provided additional details about the study area.