n.
or fish duck
Any species of the diving duck genus Mergus .
Essentially freshwater birds, they are classified as a sea duck (tribe Mergini). Mergansers have a long body and a narrow, serrated, hooked bill for catching fish. The males of all but the common merganser, or goosander ( M. merganser ), are crested. The common merganser, the hooded merganser ( M. cucullatus ), the red-breasted merganser ( M. serrator ), and the smew ( M. albellus ), a small, compact merganser with a short bill, live in northern regions; the only southern species is the Brazilian merganser ( M. octosetaceus ). Mergansers are called trash ducks because their flesh is rank. See also shelduck .