When can my chicks go out in the big girl coop?

Y'all.  We need to get serious about moving our little dinosaurs into the big girl coop.  Our babies are 6 weeks (and a couple days) old, and they are huge.  Well, just Hazel is huge.  The others are more reasonably sized.  I was looking back at pictures of our first set of chicks, and I'd estimate that Hazel is about the size they were at 9-10 weeks.  She can touch the screen on top of the brooder without jumping.  She definitely needs more room.

The littles' first trip to the big girl coop

The big girls moved into the coop when they were just shy of 6 weeks old.  Of course, for them, it was June.  And we didn't have the winter that lingered forever.  I still worried about them.  I know I keep telling you that chickens don't need supplemental heat because they're built for the cold, and that's true, but the key concept is that chickens don't need supplemental heat because they become acclimated to the cold.  If the temperature suddenly dropped 30-40 degrees, they might be in trouble.

Our chicks are acclimated to 62-68°F, because they live in our house.  Putting them outside right now, when our lows are still going below freezing, without heat, could be dangerous.  I suspect they would actually be fine, but I don't think I would sleep.

In addition, chickens are territorial, and pecking order is a real thing.  They look all cute and fluffy from a distance, but they are ruthless.  If we put the littles in with the bigs right now, the littles could get pecked to death by the bigs defending their territory and resources.  Most of the information I've seen suggests introducing littles to bigs in a way where they can see, but not touch, each other.  That way, the bigs become familiar with the littles, and by the time they're put in together, the bigs think the littles have always been there.  The other option, of course, is to introduce the two groups when they are all closer in size.  That is not an option for us, because there is no way we can keep these chicks inside until they're 14-16 weeks.

Toasty Crunch (in the background) was quite vocal in her displeasure

A third consideration is food.  The big girls are eating a 16% protein layer feed, while the little girls are eating an 18% protein starter/grower feed.  The little girls shouldn't eat the layer feed because the extra calcium could damage their kidneys.  They also still need the higher protein because they're still growing.  The big girls could probably eat the starter/grower feed, but they need the calcium from the layer feed.

One solution would be to make layer feed available in a location where the littles can't reach it, and grower feed where the littles can reach it, but in my experience, if there is food, chickens will eat it, regardless of how difficult it is.  Another solution would be to serve an all flock feed.  It's formulated for poultry that is 7-8 weeks old or older, and has the higher protein of starter/grower feeds and lower calcium than layer feeds.  A third solution would be to serve chick grower feed to everyone with oyster shells for calcium on the side.

When the top is off, the girls like to hang out on top of the brooder

Right.  So we need to consider temperature/acclimatization, protection/exposure, and food.

The plan is to build a pen inside the hen house or run, so that the big hens and little chicks can see, but not touch, each other (we have a dog kennel on permanent loan from my parents to use for this).  We are taking the chicks outside daily to help them acclimate (and oh boy, is that a production), and will most likely put the mother hen heating pad in the pen turned to its lowest setting for at least a night or two--longer if we feel like it's needed.  The chicks will have water and chick feed in the pen, and when the littles move to the pen full time, I'll start transitioning the big girls to chick feed.  After about a week, we will attempt integration, possibly by putting a door in the little girls' pen that's sized so that the big girls can't get through.  That way, the littles can get out, and they can also get back in and be safe if they're being chased or picked on.

When we're outside, they like to perch on me.  They avoid me and perching when we're in the house.

So the bottom line: when can chicks go out in the big girl coop?  It depends.  You need to consider temperature, protection from bigger chickens, and food.  For us, we're hoping soon.