I have 6 various breed hens that are 15 months old, 4 various that are 3 1/2 months and 2 Khaki Campbells (male & female). They have separate coops & nighttime runs but all free range all day. The last couple of weeks the ducks have become very bossy, chasing & nipping at the chickens when I put treats out. I put the treats in 3 separate areas, well spaced but the ducks still chase them. Is this behavior normal? Can I do anything different?