Muscovy ducks are quite large, rather ugly, and somewhat ungainly ducks. They are native to Mexico, Central and South America, but have established themselves also in parts of the US, notably Texas where we they are quite common.
This one in Hermann Park, Houston shows an attractive iridescence in the feathers.
The most remarkable feature of these ducks is the blackish or red knob seen at the bill base, with the bare skin of the face a similar colour.
Why these are called Muscovy Ducks seems to be a bit of a mystery, as they have no clear historical relationship with Russia.