I have 3 Old English Bantams, they vary greatly in size. Only 1 of them is small enough that I would attempt hatching under her. As the eggs develops the shells get more fragile, I'm afraid the 1 1/2 pound bantams would break them just sitting on them. Our smallest OEGB is just about a pound and she has a calm disposition so she wouldn't freak when working in her pen.
There are a few issues. One is chickens carry a lot of things that can kill game birds, so there is that. two, quail chicks don't seem to pay attention to chicken mothers and freeze.
I tried it with a Serema that only hatched one baby, and the quail chick refused to go under her and died. She accepted it fine, but no dice. I had them on wire so was not worried about poo.
People say they have used silkies to hatch quail, but i have never tried.
2 of my silkies decided to hide from there chicks behind the next boxes. they were missing last night and we searched for 2 hrs. Once all the chicks were out this morning, the realized they could not back out of the spot and started making noise to be rescued. Little buggers!
If anyone is interested I have a f2 oe rooster, a jubilee rooster, an ee rooster, and 2 showgirl roosters and a black silkie that are at rehome or eat stage ( well, showgirls are BQ, so they have some more time) . Also an OEGB pair. I cant bring myself to cull kazoo.

Also a young cream legbar boy ( newly abandoned by a silkie mum) and 3 F1 OE boys. I doubt anyone needs em, but its time to get the decibles down out there so I'm checking

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The F2 OE boy is quite striking. Great muffs