I hatched two chicks each from two batches of eggs -- my first attempts. Both went through an aggressive phase -- and they are Marans and Buff Orps, both breeds noted to be sweet-tempered. I don't remember this behavior from my first chix that I got at a week old - Welsummers from Whitmore Farm. I have no idea what the cause might be, either. I can;t say they ppeck ecxcept one who is fascinated with my diamond ring! But they do sort of mob me and try to get out and they all have lots of room. I figure it is a phase. These chicks were never crowded and to my knowledge have never had a bad time. Maybe thay are jot not civilized yet!