I was thinking about duck too! Do they free range in the day and come roost in a pen at night? Cause Not much would survive here unprotected at night. I have too many critters including a pack of coyotes.
Well... how to answer that, without writing three pages on duck species, class, and breed and the behaviors more or less common with each

Dabbler ducks don't roost, they just stay on the house floor. Muscovy ducks will roost, but usually the drakes are too heavy to fly. Another thing to keep in mind is muscovy duck are as different from the mallard breeds as horses are from donkeys. They can breed on occasion but the offspring is a sterile "mule" duck.
If you want really good answers, ask the questions in the duck forums. There are some folks over there that are very knowledgeable on raising ducks. I'm still learning as I go as this is my first year with poultry of any kind.