Duck Nesting in Fields of Undisturbed Grass-Legume Cover

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Abstract
A study of dabbling duck (Anatinae) nesting was conducted during 1971-73 on nine 12- to 54-ha Cropland Adjustment Program fields in the prairie pothole region of north-central South Dakota [USA]. The tall, dense vegetation was comprised of introduced cool-season grasses and legumes, primarily smooth bromegrass (Bromus inermis), intermediate wheatgrass (Agropyron intermedium) and alfalfa. Complexes of temporary, seasonal and semipermanent wetlands surrounded the fields at densities of 1.5-8.1 basins/km2 and areas of 9.4-17.2 ha/km2. Of the 620 nests studied, 38% were of blue-winged teal (Anas discors), 24% were of mallards (A. platyrhynchos) and 24% were of gadwalls (A. strepera). Densities of nests of all species averaged 67, 114 and 47 nests/km2 (3-yr av [average] 77/km2). Calculated hatching rates were 69, 58 and 32% (av 56) for the 3 yr. Hatchability of eggs in successful nests averaged 97.1%. Averages of the 4.0, 6.2 and 1.2 ducklings/ha were hatched in 1971, 1972 and 1973, respectively (3-yr av 3.7/ha).