Cannot figure out what type of duck/goose this is. Help?

I live in Eastern North Dakota and there is this duck in the pond near my house. It has been here for about a year now even through the cold winter. I have NEVER seen a duck like this before and neither has either of my parents or grandparents.

It looks like either a large duck or a small goose but is probably a duck

it's completely black except for the tips of its wings and its stomach and neck

the black part of its head is tinted green in the sunlight

its beak is a light grey

and its feet are orange

sorry i couldn't get a good picture of it