Personally I do not like ducks and chickens sharing the same coop simply because the amount of ammonia the ducks produce overnight can affect the lungs of the chickens perched above them in the house, however there are many people who successfully keep them all together with no problems at all.
If you decide to integrate ducks and chickens together here are a few tips:
Chickens perch up high, please make sure that the ducks have access away from the perches otherwise they will get bombarded overnight!
Do not keep water in the coop during the night as the ducks will turn the whole coop floor into a swimming bath.
Ducks do not normally use nest boxes, I have found that the odd old tyre left on the floor attracts the ducks to lay in one place, no promises though.
Use plenty of straw on the floor as this will help soak up the tonnes of smelly poo they produce overnight, a regular poo pick will help reduce an odour problem.
Good ventilation is a must, high enough that it doesn't create a draught for the chickens on the perch.
There isn't normally a pecking order between chickens and ducks unless you have a cock bird who will do his best to rule the roost!
Any more suggestions would be welcomed.
