I had problems with mine. I built a pen that is 3 ft. high in the front but 2 ft. high in the back so the water would run off the roof. I put a dowell across the pen to give the pigeons a place to roost. Unfortunately while the pigeons were roosted the ducks could reach them and pesture them. One by one they would pick on the pigeons until I noticed sores on the pigeons. I ended up shooting the pigeons. I will say that I had several pigeons and just 2 ducks but I bought the ducks off craigs list and they were mature ducks. I'm not sure if the age of the duck had anything to do w/ it. I have some young flyers now and have thought about adding a few pigeons to see if I get the same result. I learned that if I built something again I would make sure their was enough room for the pigeons to roost above what a mature duck could reach.
split your coop in half with the ducks on one side and the pigeons on another, otherwise the ducks will eat all the pigeon scratch(feed)..pigeons like clean water,and need dry grit... ducks like to eat their food in the water