What a nice little momma and chickies! As far as how long she stays in momma-mode, it depends on the hen... and her hormone levels. You could fix up an outdoor pen with a simple box house inside... sort of a chicken tractor. This would, by default, prolong her mothering days. I do this with my broodies and it works well. When they start getting cramped, I begin letting them free range with momma in the afternoons and then lure them back into the pen with crumbled hard boiled egg. Having the tractor located in the chicken yard helps the hen to keep her place in the flock and lets the other hens and the chicks get used to each other safely. Eventually, momma will remember that she is a hen with a LIFE, for goodness sakes! She may or may not start taking them into the big house at night. You kind of just have to play it by ear. She won't want to leave them until they are fully feathered and by then the weather will be warm enough that they won't need her at night. Usually by this time they learn to stay away from any mean hens you may have. So if she abandons them, they will still be okay in the chicken tractor until they get older. If they don't start using the big house on their own by fall, you may have to put them in a dog crate or the like for a couple of days INSIDE the chicken house. That way they will accept it as home. I've never had a brood of chicks that didn't do just fine. I've lost the odd hatchery chick, but my Sussex hens always raised every chick they hatched. They teach their babies well and equip them for real life. I much prefer natural incubation. Good luck with them and if something comes up that worries you, be sure to post about it. You might also visit Velvet Sparrow's site. I think you know how to get there, but I'll post the link anyhow. Here is a link that might be useful: Velvet Sparrow's Website - Bookmark it, folks!

Is it possible to replace the first two eggs with fresh ones, so they will all have the same hatch date? Adding the eggs you just got is risky, she may set them but abandon them when the first 2 hatch. Do you have an incubator you could finish up the eggs in if she does? That way, when the eggs hatch, you could slip the fresh chicks under her at night, adding to the ones she already has. Velvet ~:>

Congrats on the upcoming chicks! :) It's such a cool and fun experience... I agree with what fanci & snycal said...especially about 24 being too many. She can't cover that many efficiently and the hatch would be disappointing. Plus, don't forget that she has to care for all of those babies once they DO hatch! Your better off limiting the number of eggs and getting great chicks. And marking the eggs is vital if there is any chance of other hens getting in there to lay eggs and cause confusion over which ones are the ones you are trying to hatch. :) I would definetely give her her own space to brood, hatch and keep the chicks for at least the first week or two. Other hens can become jealous over either the nest and eggs or the chicks, and mama can't be everywhere at once. Eggs can get broken and chicks dead in the fights that ensue. Predators can be VERY patient and clever about getting a chicken dinner, especially at night. You need to keep predators OUT and chicks IN. If a chick slips out through a small opening, mama can't get out to protect it. Your brooder needs to be STRONG so predators can't just barge their way in, either. Make plans for safe feeders and waterers (prevent drownings), too. My chicken page has a section on broodies and chicks that may help, too. :) Have fun! :) Velvet ~:>

The reason people recommend placing chicks under a hen during the night is because she will be more apt to accept them as HERS when she wakes up in the morning and BAM--eggs gone, chicks in their place! Of course, make sure she has eggs to sit on before the chicks arrive and make the switch as smoothly as possible, with as much darkness as possible. Trying it during the day, in my experience, results in the hen freaking out and trying to get AWAY from what she presumes are some OTHER hens' chicks--she expects their real mama to come along and clean her clock. I'd have a brooder box standing by and ready to go just in case she doesn't accept the chicks. It's normal for broody hens to only come off the nest for a few minutes each day to eat, drink, poop and maybe dustbathe. Unless you are standing there watching her the entire day, chances are you won't see it. Also, to answer your other question, give the chicks something with traction for bedding/to run on. Pine shavings, straw, dirt--it's all good. Avoid slick surfaces like newspaper, which can cause the chicks' legs to splay when they cannot grip it with their feet. Good luck with your chicks, cochins make great moms. :) Velvet ~:>