I noticed a lot of my buff orps have like a shake of their head like something is irritating them. They have done this since they were tiny. There are no pest or lice etc on them, is this normal? My brahmas do not do this. They eat well and have grown and at 22 weeks have begun to lay. They sing etc. Is this a genetic thing in some or a disease that I might see the results of later. They do appear very healthy otherwise. Jean