I have 2 female ducks with babies. The first one hatched out 16, 2 wks ago ,the second hatched out 5 yesterday. They are all in a fenced chicken yard for now,the females can't fly out but the male,crested mallard,can fly in. When he does he attacks the babies and sometimes picks them up and shakes them. Is he trying to kill them or just setting boundries? Do I need to keep him away from the babies?