On the left you will see a "manky mallard," but on the right is the Pekin Duck. The Pekin Duck is a domesticated duck and isn't normally listed in birding guides. However, we spotted this one in the wild, so I'm counting it. I guess it wanted its freedom.
The "manky mallard" is also a form of the wild Mallard, but its variations come from domestication as well. Wild mallards typically have a white ring around the base of their necks rather than a white bib like you see here.