The Red-breasted Merganser  (Mergus serrator) and the Mallard (Anas platyrhynchos) belong to the same orders of ducks, anseriformes, and the same family, anatidae. The Merganser is a fish-eating duck, a great diver, and mostly stays in freshwater lakes. It is a migratory bird in Iceland.  The Mallard is a dabbling duck, it doesn’t dive but tips forward in the water to find food. It stays in Iceland the whole year but goes down to the shore in the winter time. Both of these ducks are common in Iceland.