I have a a male khaki Campbell, named Calvin and him and my two other ducks have all been fine together before. The other day I added two new girls to my tiny flock, so now I have 5 ducks total. 4 girls and Calvin. As soon as I let the new ducks with mine Calvin immediately began mating with them which I found normal, I figured after about 2-3 days he would calm down and note mate with them so constantly, but it has been a week and my new girls are missing neck feathers and im worried that he may start biting their skin and the girls will get infections or become ill. He is completely normal with my other ducks that he was raised with, it's just these two girls that he picks on. Should I separate him from them? Is this because they are so new and how long will it last?