I'm fairly new to the Muscovy duck thing as well and was thinking about moving some roosting poles from our old chicken coup to the duck run.
We have a couple of tree stumps in the run and the older (they are only 1 year!) females love to perch on them.
They are tree birds so I was thinking they would love to perch. However in the winter I have to put my guys in their little hut otherwise they get soaked to the skin with the rain we get here.
I think you should give it a go and see what your birds think
