Great post Lady...I will probably try moving my bantam next time she is broody. For the second time, I went out and found her off nest after larger hens laid new eggs in her clutch. First time it was upper 60s/low 70s so I don't think it hurt. But yesterday it was mid-upper 40s and the eggs were cool when I found them.I personally would consider moving eggs and hen as cooperative brooding has not gone well for me...dominant hens tend to chase less dominant broodies off the nest, eggs tend to get broken or kicked out and cold. The risk of moving the hen/eggs is the hen may prefer the original nest to brood and not settle with the eggs on the new nest...some are very set on the original location....others barely notice. If you think she can communal brood/nest where she is...then leave her. I have heard many doing such; I just have not had good of experience with that personally. If she'll move, then I find it best to do so...safer and less stressful for mom and babies.
As to winter hatching...I live in wet Oregon so we don't get sub zero for days on end nor feet of snow....however, I have hatched in cold winter before (and am currently having my Silkie sit on 6 Marans eggs due mid January)....we can and do get cold snaps...One February hatching was during a cold snap...clear (cloudless) and therefore cold...getting low 20's and even upper teens at night and barely making 30 during the day most days that week...I had to haul water to keep birds in liquid water (something we rarely have to worry about here in Oregon).
The things to watch out for are of course, as you mentioned, water freezing. Babies can expire quickly if they can't get water. Also, once hatched, you have to be sure your babies cannot strand themselves away from momma and expire from cold. They are amazingly apt in doing that by a blind corner, hole in the fence, hole in the wall...all manner of "stupid chick tricks" where they can get themselves into a fix and expire quickly in the cold as they will just stand there, trapped or lost, peeping like crazy while mom frantically calls back. That's the only time I've lost chicks in winter...through the trapped/lost chick syndrome. (Oh one was I think do to failure to thrive...something wrong with the chick from the get go.)
As long as they are with momma, she keeps them plenty warm. My first winter chicks dumb founded me on my first winter hatch...they ran around as if it was just fine...I was still getting heat lamp brooding ideas out of my head thinking they will surely die in this cold...don't they know they need a carefully controlled environment?....nope, they feathered in quicker, grew faster, and did just fine running around with momma in below freezing temperatures. I did have them out of direct weather, so it is essential they stay free from direct rain, snow, wind, draft.
The last item I could recommend is be aware that the sound of little peeps will draw every sort of predator out, especially in winter when there are fewer food sources. Make sure your hawk netting is up and your fencing is deep enough and doors latched tight for raccoons, cats, etc.
Because of this (and stupid chick tricks when they are really small), I keep them locked up the first week in the hutch and don't let them out into the run...this is also so that they don't get caught below while mom goes above...another favorite "stupid chick trick"...trust me it is not fun to have to round up the little peeps to put them up with mom into the coop...mom usually takes up residence below, so you have to try to move them all...and they go all different directions as you round them up. It takes them about a week or so to be big enough and smart enough to scale the ramp to follow mom back into the coop nest if you have a raised walkway from the run. If your cage is on ground floor...your worries are over (unless there is a blind corner). I crawl and poke before each hatch to make sure nothing new has opened up where they can get themselves into new trouble.
Mom and babies should be on chick feed. She doesn't need the calcium in layer feed nor do the chicks (that amount of calcium would be harmful to them). Medicated if you prefer, non if you don't but watch for any sign of coccidiosis (diarrhea and bloody poo...I'm talking frank red blood in runny poo not the stringy pink intestinal lining shed that is normal). If you're quick enough medicated feed can save the day, otherwise you'll need Corid in the water.
The other chickens will love the baby feed and gobble it up, so you'll need to keep babies and grown ups separate or fix up a feed system where the babies can get to it but the adults can't. Babies also shouldn't have access to the high calcium layer feed...or put all on a flock grower with oyster shell supplements for the layers.
I also like to start my babies first couple of weeks with the Chick-Saver vitamins and electrolytes with probiotics...and of course ACV...having a good flora in their intestines goes a long way to fend off coccidiosis and other chick hood illnesses. I like to keep my chicks separate from my flock to give babies time to build their immune systems before encountering the big chicken diseases that other birds have immunity to but which can devastate a little chick. (I introduce at 8 to 12 weeks for that purpose and for the purpose that my little momma banty gets picked on by the others...keeping them separate saves a lot of stress on her...she is a very valuable brooder for my flock.)
That's the main things I've learned through the brooding seasons.
Good luck,
Lady of McCamley
Also, 2 eggs broke. They were duds cause they smell bad with no chick growth unless it got eaten. Not sure if they "popped" (I read comments about bad eggs exploding, thought that was a joke but I am not so sure now!) or if the larger hens laying in her clutch broke them.
Either way, I have 7 remaining eggs that are due in about 1 week. With the 2 instances of short term exposure, I am getting less hopeful for success. She is a pretty tolerant gal, so next broody spell, I will find a way to move and isolate her.
I know its late, but the holiday was hectic...Merry Christmas to my friends at BYC!