We have 2 grown up chickens and got a Silkie and a Polish to move in with them around 4 weeks ago.
The Silkie seems to be holding her own but the Polish is being beaten up, his/her head feathers have just been plucked out so now it has a bloody head :(
They have been in separate runs in the daytime and we have been letting 1 of the big chickens free range with them, then they all sleep together at night (no bickering at night).
I am wondering whether now blood has been drawn, whether they will ever stop picking on the Polish and also as she seems to have started crowing 
whether she is actually a boy and that's why they are not accepting her (the Silkie is not being attacked).
Any thoughts/help would be appreciated.