Description:  This is a diving duck. One of its most noted visual characteristic feature is the long red bill on both male and female. The male has a green head, but otherwise a lot of white. Female has more of a crest, reddish brown head and a white spot on its chin and neck.

Habitat: They like large deep lakes where they can dive deep.

Diet: Usually just fish. 

Range:  The species is a partial migrant, with birds moving away from areas where rivers and major lakes freeze in the winter, but resident where waters remain open. Eastern North American birds move south in small groups to the United States wherever ice free conditions exist on lakes and rivers; on the milder Pacific coast, they are permanent residents. In Arizona, they like Patagonia Lake, Parker Canyon Lake and Cochise Lake, but can be found on smaller lakes while passing through.

Breeding:  They nest in tree cavities. The female lays 6–17 (most often 8–12) white to yellowish eggs, and raises one brood in a season. The ducklings are taken by their mother in her bill to rivers or lakes immediately after hatching, where they feed on freshwater invertebrates and small fish fry
  
Fascinating Facts:  These large fish-eaters have serrated edges to their bills to help them grip their prey. Along with the Smew and the other Mergansers, they are often known as "sawbills." Common Mergansers are the largest of the three merganser species in North America.