Typically you should be fine putting a few ducks in with your chickens. They sure can be messy though! However, as long as you don't mind changing their water a little more often than you will be fine.
I have several ducks in both of my coops and they eat the same food and even free range with the chickens. All my birds get layer pellets.
I would probably suggest brooding the ducklings separate from the chickens though, as the ducks typically need less heat and will wet the bedding and chicks very quickly! A chilled chick will will have a greatest chance of dying. However, both chickens and ducks require very similar care.
Cayugas are BEAUTIFUL! Especially in the sunlight. Good luck if you decide to get any! Ducks can be a lot of fun.
