I've had my girls peck me too hard when both hands are occupied (why do they think I'm a roost?). If they are close enough to me, I blow forcefully into their face and it startles them enough to stop. When the hands aren't otherwise occupied, I also peck them back. My Buff Orpingon, Cashew, is my primary offender. I think she does it to get attention as she is jealous of the Dark Brahma. Who would have thought chickens were this complicated!