If I speak to them they give a little rapid shake of the head. I experimented with this: if I speak in a low voice they shake their heads. If I speak in a high voice they shake their heads. If I am loud, they do it, and if I'm quiet they do it. Some do it a lot, and some do it rarely. Sometimes it's funny- I walk into the henhouse in the evening when they're all roosted, and I say "OOOOHHHHHH" and practically EVERY CHICKEN IN THE ROOM SHAKES HER HEAD AT THE SAME TIME! I have no idea why they do it! You try it, I'm curious to see if yours do the same! Has anyone ever heard of this behavior before, and if so, please explain!!!!!