They're fully feathered in about five to six weeks! Nice to be in touch with recyclable wood, huh? Great! I will be able to answer some construction and necessity questions you may have! It's a good idea to get them around the same age!
The older chooks might hackle your chicks if they still have down. I know my Silver Leghorn chooks hackled my Barred Rock chicks when I first got them. Hackling is when the bigger bird tries to get the smaller one into submission. No one is hurt, but it does look aggressive. They'll continue to hackle even when they're all grown up! It's like campaigning, the bird gets as high a rank as it can in what is called the Pecking Order so that it gets first dibs when a hen to the nests, feed, and sleeping areas. That's why roosters fight, sometimes even hens will fight, to get the other into his place in the Pecking Order.
When a rooster is matched he will fight to the death! Don't let that happen! I once left for a day drive to a place two hours from where I live and when I came back one of my Cockerels, Grizzly, was limping and died the next morning!
This is a picture of him before his death (He's a New Hampshire/Easter Egger cross (Note the redish feathers))
And here is the killer, Valentine, a typical Rhode Island Cock! (Not a well maintained Rhode Island, not very red)
I'm not using them for breeding, so I'll only have one rooster, that being my ayam cemani. (If any mixes do come of that from my other hens, I'm curious to see) my 4 weeks still have a bit of down, though phoebs is a bit feisty and I'd like to see anyone try to hackle him lol
Oh I had a little fighty RIR and he was pounded by the other cocks. Though you got a point, because he later zeroed in on one twice his size and made him peep miserably!
I used to have a rir cock that attacked me and the other cocks I used to have he was a real bully!! So what I did was let my game cock handle him and he never bothered anyone ever again.