A light and very quick cuff across the head when he bites should suffice. Not a slap, mind you...a cuff. It surprises more than it hurts and doesn't knock the bird around, just reminds him that the behavior brings an undesirable response. Worked for my roo and it didn't have to be repeated. Biting is not like flogging or threatening behavior, it is a quick response to defend a hen or himself. It rarely has anything to do with hormones....a hen will bite sometimes if you reach for an egg or chick.