I have 2 silkies, 4 black australorps and, a barred plymouth rock. Last week my Silkie Lucy got picked on by the big chickens and a whole patch on her back was missing feathers and bleeding. She is fine now but we seperated them so that the little ones are together and away from the big ones...
So I have four black australorps all 19 weeks old and one of them is less developed but has a different tail so I don't know if it is a rooster or not.