If you visit the refuge in fall, it is very common to see a raft (large group, possibly hundreds of thousands) of canvasback ducks stretching for miles near Ferryville, Wisconsin. The canvasback is a duck that forages by diving to the Mississippi River bottom and grubbing out the wild celery tubers, a nutrient rich enlarged part of the plant.
Other common diving duck species on the refuge are the lesser scaup (commonly referred to as bluebills), common goldeneye, ring-necked duck, bufflehead, ruddy duck, and mergansers (hooded, and common). Their wings are relatively small compared to their body size, so divers must use rapid wing beats when they fly, and when launching into flight, most of this group patter along the water before becoming airborne. Divers have large feet, placed well back on the body and are not agile on land. They dive, sometimes to great depths, to feed on aquatic plants, fish, clams, and snails. Favorite diving duck foods on the Upper Mississippi River are wild celery tubers, sago pondweed, fingernail clams, and snails.