Under about two weeks, and we snuck the chick into the nesting box. She came back and circled, puffed, low bwoooooooop wop wop BAM! I grabbed the little one and shooed her away as soon as I saw her move fast, but it was too late. Little one got to kick it in a bird cage away from her buddies till the scab fell off.
My theory on what went wrong is that I don't think a broody is always "broody."
We had to isolate a hen in the dark to slow/stop egg laying recently for a mild prolapse, and it got me thinking, broodiness might not necessarily be a "mothering" thing, but an egg laying thing. The hen stays in a dark place and slows/ stops laying - goes off food, which also slows/stops laying, so perhaps this is natures way of taking a potentially ill hen, and putting her off laying for a time while she recovers. Nutrition is my theory regarding this particular hen, since she had been getting more treats than layer feed.
So the question comes to mind, was she truly BROODY or was she feeling under the weather? This is a hen that appears to go broody at the drop of a seed. Every other month or so. So even thinking more about this, breaking a brood, and putting her back to egg laying might actually be damaging to her system if she might be having a problem that isn't enough of a problem to make her behave noticeably ill, but just enough to make us silly humans go "awww she wants babies!!!"
Once the chicks grew, this particular hen is now second to last (just above the one she neck ripped) from the bottom in the pecking order, so I think there's something up with her, she was someones pet before she was part of a flock. Now that I have the others behaviors to compare her to, she is neurotic, which could be nutrition. We have everyone completely off treats right now and nobodys broody, nobodys prolapsing. Egg shells are harder and egg eating is non existent.
I've had much better success with crate/lamp brooding, giving the newbies their own space in the coop/run once they fledge where they can see the bigguns and the bigguns can see them and then turning them loose once they're 3/4 or more the size of the bigguns. We've done it twice that way after the failed experiment and aside from a few pulled tails and getting chased for a bit, it seems to be the most peaceful way we've come up with.