I just had a 7 month old barnyard mix hatch and raise a few chicks. They're 6 weeks old and she's still taking care of them.That wasn't even the worst part! There were usually multiple hens in the nest at the same time ... and they would also play "Pass the Potato," literally stealing eggs out from under their neighbors.
I actually watched one pullet roll a "stray" egg a good three feet to where she was hiding hers. At that point, I gave up trying to keep track!
When the eggs were far enough along to reliably candle, I pulled them all. Surprisingly, almost half survived the games! Call me weak, but I can't toss obviously developing eggs. I pulled the two most persistent Mamas and moved them to a rabbit hutch with the remaining nine eggs. Out of 20+ eggs with five Mamas, I got four really nice youngsters.
Lessons learned:
- When everyone is in peak laying mode, gather twice a day.
- Check ALL corners for eggs, because the little monkeys roll and hide them.
- Never, EVER count on a newly laying pullet to abandon the nest!

I have 5 Buff Orpingtons, only one laying, and 5 Cochin Bantams.
I can't wait for them to go broody <<< famous last words, lol