I have a mixed flock of 7 six week old chicks. All are pairs except my EE whose buddy didn't survive the trip via USPS. I have 2 RIRs, 2BRs, 2 Anconas and 1 EE. We've noticed that while they have always been together the like breeds stick together. My EE is the odd ball and the most skiddish and independent, so she seems okay with not having a buddy. The others though tend to stick really close together, sleeping and eating as pairs (for the most part). I find this rather fascinating, so I am wondering if they recognize their own breed and how that is. All of my girls are the same age and roughly the same size. Obviously they differ in color, but even my BRs and Anconas have similar coloring and they know who their partner is.
I have 10: 4 RIRs, 5 white (in told probably white leghorns), and 1 bantam Cochin frizzle. They mostly seem to mix, I almost never see the reds on their own and the whites on their own and there are usually one of each hanging out with (looking after) Snoodle (my frizzle).
That's another thing, they seem to all look out for each other. If one starts peeping loudly/distressedly, several (if mot all) will come running, esp if the one yelling is Snoodle.