Ducks can be raised for both meat and egg production. Selective breeding has developed breeds of ducks (e.g., Campbell and Runner) that are excellent egg producers. Other breeds are most suited for meat production. Some duck breeds are kept simply as ornamentals for poultry shows or ponds.

All the ducks breeds raised today (except the Muscovy, which is not really a duck) are descendants of the wild Mallard. The Mallard is the only wild breed of duck that has curled sex-feathers on the tail. The sex figures are two hard, curled feathers growing from the upper portion of the tail in drakes (male ducks). These feathers grow upward and forward.

The Muscovy duck is the only 'duck' that is not descended from the Mallard. The Muscovy is actually a distinct species. Muscovies are from the southern hemisphere (Mallards are from the northern hemisphere), specifically in the mountainous jungles of Peru, Brazil, Bolivia, and Ecuador near the headwaters of the Amazon river. The Muscovy has a body like a duck; it nests, attacks predators and hisses like a goose; it roosts like a chicken; and has a plump breast like a turkey.

Selecting the right duck breed (University of Kentucky)