[ErikCorry]

IME ducks don't go into the coop at dusk so they will get trapped on the wrong side.

[Rendello]

Most ducks lack the roosting instinct that chickens have. Apparently Muscovy ducks are a notable exception, they'll roost in coops, on roofs, and in trees like chickens do.

https://en.wikipedia.org/wiki/Muscovy_duck#/media/File:Musco...