Is this a serious question? All birds have a cloaca, inside this cloaca is a 'collection' site where the anus etc; meets, the vagina also ends at this site.
Everything goes out the same home.
The penis in males also sits in here and can protrude with some duck species, but mostly copulation is reached with a rubbing action.
Now boy, stop staring at your ducks *** and go find a good hobby!
