I have a roo that has started to 'shake' his head side to side, as to say 'no no no' like he's trying to shake something off. I cant find any mites, fleas or bugs. He is in a beautiful coop, clean all the time, and has a large pen with pine trees, shade, grass, etc. to play in all day. Gets DE in his dust bath, floor shavings, etc. ANy clue?????