I was just wondering about this recently too. There are multiple generations of birds in my free range coop, and some of the breeds have birds that are different ages, or were added later. I have 28 chickens in my free range coop right now, 4 are roosters. The split is, 6 Ameraucana(1 Roo, 5 Hens), 5 Cuckoo Maran Hens, 5 White Crested Black Polish (1 Roo, 4 Hens), 3 Black Crested White Polish (1 Roo, 2 Hens), 3 Mottled Houdan Hens, 2 mixed breed Hens, 2 EE Hens, 1 Splash Polish Hen, 1 Buff Laced Polish Roo, and this is what I've observed:
- Everyone seems to mix up or be solo when they are doing 'serious' foraging, but when they are wondering in a casual relaxed sorta way, dust bathing, or just taking a siesta, I notice some definite grouping with the Cuckoo Maran Hens(sisters, so understandable), the Trio of Black Crested White Polish, and the mottled houdan hens (1 is a year older than the other 2).
- There seems to be a pattern in my flock when it comes to who breeds who. I always assumed the roosters would mate with anyone that would let them, or they could catch, but my birds seem to be prejudice, or respectful of their fellow Roo. My Alpha Rooster "Will" the Blue Wheaten Ameraucana has chosen as his own, the 5 Ameraucana Hens (1 white, 2 Wheaten, 1 Silver Wheaten, and 1 Silver), the 2 EE hens, and the 2 Mixed Breed hens. I have never seen him mate with any of my polish hens, they don't even seem to catch his eye. I thought maybe it was because of size, but interesting enough, he doesn't seem to have any interest in the 5 Cuckoo Maran hens, which are similar in size to his girls. The Polish Roosters don't even try to mate with anyone other than the Polish Hens, or at least I haven't seen it. And to back this up, I incubated 23 eggs in March (10 from my Ameraucana Hens, 6 from my Cuckoo Maran Hens, and 7 from my Polish), after the first candling I found 7 Ameraucana Embryos, 5 Polish Embryos, and nothing in the Cuckoo Maran Eggs. At Hatch time, I got 11 chicks, 6 Ameraucana, 5 Polish. There is no possible way that any of these Chicks are crosses just from how they looked then, and even more so looking at them now.
- Lastly, I noticed that in the Posts where people weren't noticing pairing, they seemed to be mostly people who's flocks were all singles of each variety, and 1 Rooster if any. (I think the roosters have a lot to do with the groupings if there are any)