Last month we adopted 30 baby chicks, 20 Easter Eggers at about 1 week and 10 Silver Laced Wyandottes at about 3 days. These were out first chicks EVER and we were really excited. They were in a cardboard brooder without a thermometer, just judged by how the chicks were behaving. They got non-mediated Purina feed and had straw bedding. However, a few weeks ago, the Wyandottes started picking out the rapidly developing tail feathers of the EE's. I had little stumpy bloody tails all of the place, and had to separate quite a few. A few days later, we noticed that one of the Wyandottes had swollen and bloody wattles, and I saw other chicks (mostly EE's) picking at them. Finally, the EE's got feathered enough to remove from the brooder, and the majority of cannibalism stopped once they were separated--only one bloody tail and one wattle problem since. Recently, when I tried moving the Wyandottes in with the EE's, the wattle-picking happened all over again (though the EE's are too big for the Wyandottes to mess with them). I ended up separating the EE cockerels from the group, and that solved all the problems. An interesting fact is that our EE's don't really have wattles. The Wyandottes are also a little short on tail feathers. What I'm wondering is, what are some reasons that this happens? Could it have anything to do with the "strangeness" of the Wyandottes' wattles to the EE's? Or was it just boredom? Is this why you're not supposed to mix age groups? Another note is that 26 out of 30 of these chicks are cockerels--could that generate all the aggression? Thanks for any advice!