This is my first flock. Three chicks, two light brahma pullets (I hope) and one Black Australorp cockerel. They are only 4 - 5 weeks old and still in the indoor brooder. They will be there until the coop is finished/delivered in two weeks. Anyway, when they are inside in the 3 x 2 brooder they get along famously. I have observed no pecking or aggression. When we take them outside (daily for 1 - 3 hours) they get to free range the yard. Mostly they just follow each other around scratching in the dirt and grass. Occasionally though, the cockerel will suddenly run over to one of the other chicks and kind of stand up all tall and puffed out - almost like a challenge. There is no pecking, but it seems sort of aggressive. A couple of times he's done that and the other chick will sort of challenge him back. I can't explain it exactly. My better half thinks it's just play. I think I agree, but want to make sure that things are groovy for the chickens. The cockerel is going to be re-located in a couple of weeks (he's illegal here). I'm going to miss him a lot. We're getting three to replace him (ha ha). Thanks!