Any bird of the genus Mergus
), and allied genera of the subfamily Merginae
. They are allied to the ducks, but have a sharply serrated bill, eat fish, and dive for food. Also called fish duck
. [1913 Webster
" The red-breasted merganser (Merganser serrator) inhabits both hemispheres. It is called also sawbill, harle, and sheldrake. The American merganser (Merganser Americanus.) and the hooded merganser (Lophodytes cucullatus) are well-known species.