Pied-billed Grebe

Pied-billed Grebes are common waterfowl often mistaken for ducks. They are taxonomically separate from Anseriformes, though, and belong in their own family, Podicipedidae. They eat aquatic animals (fish, frogs) and have a long, undulating call.
Basic-plumaged bird on the left, alternate-plumaged bird on the right.