The Common Merganser (Mergus merganser), also known as the Gulaund or Goosander, is a species of duck that is found in Europe, North Asia and North America. It is most commonly found on lakes and rivers. North American birds migrate south in small groups to the United States where ice-free conditions exist. On the west coast, some populations are permanent residents. Scandinavian and Russian birds also migrate southward. Most western European birds are resident. Three subspecies are recognized.
Sexes are easily distinguishable, since the male merganser has a dark green head, and the female has a reddish-brown head. The bills have serrated edges to help them grip their prey. These ducks, along with other mergansers and the Smew, are known as “sawbills”. Some common historical names given to the merganser include Sawneb, Jacksaw, Dun Diver, Harle and Rantock. The Common Merganser is 27.5 inches long with a 30 to 37 inch wingspan.
The diet of the merganser is fish, mussels, and shrimps. The young mainly eat aquatic insects. This bird nests in tree holes.