The refuge provides important year-round habitat for migrating and breeding waterfowl, the numbers of which are especially impressive in spring. Once the refuge’s managed impoundments (viewable from the Liberty Loop trail) are ice free, large numbers of waterfowl begin their northward migration. At its peak, two to three thousand Northern pintails, two thousand green-winged teal and up to one thousand ring-necked ducks can be found here. These are joined by smaller numbers of blue-winged teal, American black duck, mallard and Northern shoveler. Also of interest are the occasional redhead, canvasback and tundra swan. Mallards, wood ducks, green-winged teal, mergansers and black ducks remain as summer residents.