My normally sweet natured cockerel has given the 3 chicks a peck in the past but now they are 11 weeks old, he is really chasing them, pecking and trying to kick at them. I could understand it if they were cockerels but I am sure one is a hen. They all free range during the day where there is plenty of space for them not to be on top of each other but I have had to separate them away from him when they are penned in for the night. Is this normal behaviour? I am new to chick rearing.