The seaducks (Mergini) are a tribe of the duck subfamily of birds, the Anatinae. The taxonomy of this group has not been entirely worked out. Some authorities separate the entire group as their own subfamily, others remove some genera from the group, and keep others. Most species within this group spend their winters near coastal marine waters. Many species have developed specialized salt glands to allow them to tolerate salt water, but these are poorly developed in juveniles. Some of the species prefer riverine habitats. All but two of the 20 species in this group occupy habitats in far northern latitudes.
The fish - eating members of this group, such as the mergansers and smew, have serrated edges to their bills to help them grip their prey. These are therefore often known as "sawbills". Other seaducks forage by diving underwater, taking molluscs or crustaceans from the sea floor.
