Ducks carry a number of things that could cause a chicken to get sick, because they are not used to coming into contact with those microbes. If you are making sure the chickens have access to clean water and fresh bedding, there is not much more you can do. Just give electrolytes to the sick ones in isolation, if it doesn't get better within 5 days, you should put them down. However, you don't have to cull your flock. Those that don't get sick will be stronger for it. You will always run the risk of losing a new chicken when you have mixed flocks. I choose not to house them together so that my chickens always have somewhere special haha. But one of my Swedish really enjoys laying eggs in the chicken coop. Apparently, she can climb the ramp! I also give them a very large run, a fifth of an acre for 16 birds, half water and half land. Older birds have a harder time adjusting than strong, younger ones. Also, I don't recommend brooding them together. It's messy! Ducks never cease to amaze me with their antics and messes! It's best to wait until they're ready to go outside where there can be plenty of space. Okay, I'll stop rambling! Sorry!
