Black duck?

That’s defantly a very interesting duck. I think it might be a Mallard cross with another species but Im not completely sure yet

Manky Mallard ;-)

Im sure it’s a Mallard. Just not sure weather it’s possibly a cross or hybrid or not, I still think it might be a cross or a hybrid. A Mallard that looks a little usual tends to be a cross or a Hybrid.

It's called a "Manky Mallard" Zo

probably as good as it gets Linda though no bird deserves the moniker "manky" in my opinion

Very true Pete...Feral Mallard do? Lol

Thats ok. Also about the Cayuga Duck  is this what  you meant? 

https://www.waterfowl.org.uk/domestic-waterfowl/heavy-ducks/cayuga/

Ah yes, it looks very similar, especially the sheen on the feathers and the colouring in the same places. Thank you.

It is just a crossed bred Mallard though