Small aquatic insects and other invertebrates associated with marsh vegetation are a major source of protein for newly-hatched ducklings . Adult waterfowl feed primarily on aquatic plants during the summer and waste grain on surrounding agricultural land during fall migration. The redhead duck, canvasback duck, and other diving birds such as eared and pied-billed grebes construct overwater nests. Dabbling ducks such as the mallard, blue-winged teal , and northern pintail nest in the grasslands, but use the marsh to rear their broods. Man, too, benefits from marshes .
Wetlands serve as reservoirs, storing potential floodwaters and providing recharge of groundwater.
They also serve as natural filters to improve water quality. Unfortunately, the wetlands that once dotted the prairies have been and continue to be drained as a result of intensive agriculture. Ironically, drainage not only destroys the wetlands actually drained, but can also shorten the life of wetlands located miles away. For example, wetland drainage in the refuge's watershed has hastened runoff, accelerated erosion of soils, and caused additional silt to be deposited in refuge river marshes. The problem is sever enough to threaten the continued existence of marshes.