Hi, welcome to the forum! Glad you joined!
I'm not sure exactly where you are in New Zealand. You are in spring but it may still get pretty chilly at night. I don't know what microclimate you may have.
You are dealing with living animals so you do not get guarantees as far as behaviors. Anything can happen.
When I have a broody hen I often start some eggs in my incubator at the same time I put eggs under her. That way she typically has chicks to raise even if something goes wrong her brooding or with the incubator. If both work she gets all of the chicks. It can sometimes take me a week to gather enough eggs to start all of them at the same time. That means my broody hens have sometimes been broody for 4 weeks before any eggs hatch. I've never had a broody leave her nest before those 4 weeks are up once she has committed to being broody. Yours has been broody for 2 weeks, she is committed.
While I cannot give you any guarantees about what your broody will do, I would not hesitate to give her the six eggs and I would expect her to hatch them. I would plan to leave them with her and let her hatch them. Your odds of her accepting them are pretty good even if you hatch them in an incubator but they are better if she hatches them herself.
Alternatively you could candle the 15 eggs and discard any that are not going to hatch. If you are comfortable she will be able to cover all of the chicks when they are 3 or 4 weeks old in your weather you can put what is left under her if you are still worried about the 4 week thing. I would not be but I'm not you.
Good luck and let us know how it works out.
Some hens could easily cover 15 eggs. A hen hid a nest and brought out 18 chicks, which she successfully raised. I never found her nest so I don't know how many eggs she started with. On the other hand, a hen had trouble covering 12 eggs (which is what I typically give a broody) so I took 2 away. In cold weather I typically give a hen fewer eggs (8) on the theory that as they grow she may have trouble covering all of the chicks on a cold night.
I'm not sure exactly where you are in New Zealand. You are in spring but it may still get pretty chilly at night. I don't know what microclimate you may have.
You are dealing with living animals so you do not get guarantees as far as behaviors. Anything can happen.
When I have a broody hen I often start some eggs in my incubator at the same time I put eggs under her. That way she typically has chicks to raise even if something goes wrong her brooding or with the incubator. If both work she gets all of the chicks. It can sometimes take me a week to gather enough eggs to start all of them at the same time. That means my broody hens have sometimes been broody for 4 weeks before any eggs hatch. I've never had a broody leave her nest before those 4 weeks are up once she has committed to being broody. Yours has been broody for 2 weeks, she is committed.
While I cannot give you any guarantees about what your broody will do, I would not hesitate to give her the six eggs and I would expect her to hatch them. I would plan to leave them with her and let her hatch them. Your odds of her accepting them are pretty good even if you hatch them in an incubator but they are better if she hatches them herself.
Alternatively you could candle the 15 eggs and discard any that are not going to hatch. If you are comfortable she will be able to cover all of the chicks when they are 3 or 4 weeks old in your weather you can put what is left under her if you are still worried about the 4 week thing. I would not be but I'm not you.
Good luck and let us know how it works out.
