Hello Chicken Hatching Experts!
I was hoping for some specific advice? We have a first time broody Polish hen. She has been sitting for about 4-5 days on non fertile eggs. I want to get some fertile eggs for her to hatch and be a Mom to. The thing is, I have never done this, and I don't want to skip any steps and lose any babies. Just some relevant info to help you; we live in California and it's spring, so it's relatively warm here. Our backyard flock consists of 5 hens: 2 are big girls (RIR, Americauna - both very domineering) and then we have our a banty Millie, silky, and our
subject (Ms. Lady Gaga, our soon to be Polish Mom). They are all about the same age, all are laying and only she and our silkie have ever gone broody. So, here are my questions:
***This is her first broody period.
1. She is in a communal next box, should I try to move her? Should she be in a solitary environment (babies also)? I worry this will break her, or freak her out.
2. I am going to get about 4-6 fertile eggs, half from one person and half from another (2-3 days apart), do they only start to develop once they get to a certain temp under the hen, or do they need heat as soon as they are laid? I assume they don't start development until they are heated up to a certain temp (being that people can ship them and such).
3. How can I make sure they are in fact fertile eggs, and are ready for hatching?
4. Can I put the first few eggs under her and then add the rest a few days later? In the chance that they do hatch, I don't want the ones who still need a few more days to get nixed.
3. If I do place the fertile eggs under her, will she lay on them until they
all hatch, or will there be a chance that a week before they are due, she could suddenly decide she doesn't want to sit anymore? (given I am not sure how long a hen will be broody)
4. How can I check them half way through to see if they are developing right?
5. How many chicks can a polish handle?
6. If she doesn't hatch her eggs and they die for some reason, can I put 2 day old (feed store) chicks with her and she will adopt them?
7. Is there anything else I should know, or do to lower the risk of egg/chick mortality?
I am sorry for so many questions, I just want to make sure I make Momma chickens baby making experience her best

I am so excited to do this with her!
Kindest,
Lea