Ducks are divided between several subfamilies. Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water. Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules, and coots.
A Grebe is a member a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter.
Coots are medium-sized water birds that are members of the Rail family. Coots have predominantly black plumage and unlike many of the rails, they are usually easy to see, often swimming in open water. They are close relatives of the Moorhen.
Swans usually mate for life, though "divorce" does sometimes occur, particularly following nesting failure. The number of eggs in each clutch ranges from three to eight. There are six to seven species of swan.
The word Goose is the English name for a considerable number of birds. This family includes Swans, most of which are larger than true geese, and ducks, which are smaller. A number of other waterbirds, mostly related to the shelducks, have ""goose"" as part of their name.