Well, just my expierence this summer with about 12 broody pullets sitting at different times throughout the summer:
Out of 12 broodies that all sat on minimum of 4 eggs each I only have 1 live chick.
It was a crazy summer to say the least!
Most of them ended up crushing the chicks after hatch, I had 1 psycho killing pullet, and I figured out what was happening when the eggs would just dissapear, then the last egg hatched and I witnessed her brutally attacking this chick. I did everything I could to save it’s life, however the psycho pullet had already scalped this baby so badly it didn’t make it.
The one and only chick still alive was a single egg left after psycho pullet. I gave the egg to a expierenced hen who had just turned broody.
I had only 3 broody breaker cages available, so I had to pick and choose who I put in there.
I learned a hard lesson. I will not allow new girls to sit on a clutch of eggs again.