From left to right, Dizzy the duck, Poly and Princess. Poly is the chookie in question. I bought her when she was 3 months old. She is now around about 5 months old. Princess is the same age as her and yet Poly is almost twice the size of her! I have seen, lately, Poly chasing Dizzy and Princess around the coop, very aggressively. I wondered if maybe Poly was a rooster but she would have started crowing already. Anyone have any idea why she does this?