I have a male and female pair of pekins and a male and female pair of muscovy. They have been together since they were a day old and are now 3 months old. The male muscovy has recently started to attack the male pekin and tries to ride him. He's fairly larger then the rest and I'm concerned he will hurt or even kill the pekin. Is this a phase or will he continually become more aggressive with age? He immediately stops the behavior when I go near.