Chocolate runner duck gender?

[Winslow]

We got a chocolate runner duck 8 weeks ago and it's getting a greenish bill and where a speculum would be on a mallard it has a shade of green. Then we thought we saw green on its head so I was wandering if the duck is a drake or a hen

 

[TLWR]

Does it quack? Or does it sound like it has smoked a pack a day for years?
quacking will be a girl
smokers quack will be a boy