These birds only lay in the springtime, to early summer, so it won't really matter what age they are because they will be ready by time season gets here. The reason the birds loose the feathers on their backs isn't from picking, it is from piling. Chuckars are very bad for this, and really don't take confinement well. You really need space for these birds if you want them to not pile, and that goes for adults too. One thing though, they are very hearty to the cold, mine stay outside year round, and never go into my shelter for them. They also prefer to sleep on the ground, not roost. If you keep an area that will keep the snow level reasonable, you will be fine from what I have seen here. I know you get worse weather than me, but I still think they will be ok, maybe put some straw down for them or something to help out, and provide some wind breaks too. Either way, even keeping a few in a small environment, they will still pile up, that is why it is best to get them on the ground. Hope this helps!