Most domestic breeds are descended from Mallards and bred for meat or eggs rather than as pets or ornamental ducks. Many breeds are white with yellow or pink bills and orange legs.
Some retain a degree of wild Mallard colouring. Most drakes retain the curled up tail feathers of the Mallard drake.
The domestic Muscovy (and its hybrids with White-winged and Comb Ducks in some regions of South America and the Far East) is the only domestic duck not descended from Mallards.
Rouen Ducks are ultra heavy domestic ducks bred for their meat (the above ducks are for display only). Their Mallard ancestry is obvious both on male (left, centre) and female (right).
Call Ducks: unlike the heavy ducks bred for meat, Call Ducks were bred to be small and noisy. Their purpose was as decoys to "call" wild ducks out on to the water to be shot by hunters.
Many today are purely ornamental. The middle photo above shows the curled tail feathers from the Mallard drake.
Abacot Rangers (Hooded Rangers) showing the Mallard blue wing "speculum"
Thought to be a Pekin duck
Breeds of domestic duck likely to be found in UK include:
Abacot Ranger (also Hooded Ranger, above), Ancona, Australian Spotted, Aylesbury, Bali (crested Indian Runner), Black East Indies (see link below), Blue Swedish (also Swedish Blue), Buff Orpington (also Buff or Orpington), Call (above), Campbell's (Dark, Khaki), Cayuga (large version of Black East Indies), Coast, Crested (see below), Duclair, Golden Cascade, Hook Bill, Indian Runner (below), Magpie, Minature Appleyard, Mule (Muscovy/Mallard-type cross), Muscovy (below), Pekin, Rouen/Rouen Clair, Saxony, Silky, Silver Appleyard, Silver Bantam, Welsh Harlequin.
Blue Swedish, also called Swedish Blue (on right)
The Mallard influence on these is clear (hybrid Khaki Campbell?)