A black duck

I stopped by the local pond today to see about taking some photos of the geese on the water as the light was really nice but I found this black shiny duck instead.  She looks brown close up but from far off she was black.  She never moved and I got about three feet from her..obviously she was hoping I would have something to throw her to eat!  I say she is female because the male would have some blue on its wings and she did not..why is the male always prettier!?