this is my first time raising chickens I have five buyff Orp hens five white leg horn hens & three white leg horn Roosters . they are all 14 weeks old & they free range in my back yard all day and then I close them in there run and of course they go in there hen house. all of a sudden two of the roosters started biting some of the hens behind the head real hard . I am planing on culling two of the rooster . my qustion is . is this how they catch them to mate with them they really bit them realy hard is this normal I thought they would n't start that untill they were about six months old . any anwers would be appreciated.