We have had chickens for several years. Right now, we have two maturing roosters in our flock. We just got ducklings for the first time and had planned to keep them with the chickens after reading up on keeping a mixed flock. However, our roosters got very tense when we put the duckling brooder in the coop, and I'm afraid the roosters will try to bust in and attack the ducklings. Is this something to be concerned about?