I also have a dilemma. I purchased 12 different colors of English Orpington eggs for my broody hen. The seller sent 18! WOW! Hoping for the best possible odds for the Orpington eggs to hatch, I purchased an incubator. Well, chicken math got the best of me when I got the incubator home....I added more of my own eggs. We are at day 17 for broody and incubator eggs. Nine are under the hen (all viable at last check) and 19 viable in the incubator. I thought my fertility was low, so I was not planning on that many in the end. Guess I was wrong!
My plan was to move the incubator chicks in with the broody to adopt (hopefully) as they are all due at the same time. So potentially there could be 28 chicks IF they all make it through hatch. Do you think the hen can handle all of them? She is a cross between my Light Brahma hen & Appenzeller Spitzhauben rooster. She is fairly large, but not huge like her Brahma mother.
Our temps overnight have been in 50s - 60s.....she has her own coop/house about 8 x 8 fully enclosed and fairly draft free.
Opinions please....can she handle 20+ chicks?
Is she an experienced momma? If not, then I always error on the side of fewer. (and I generally try not to use a first time momma with purchased eggs).
28 is a lot even for an experienced momma, but full size hens with plenty of fluff have hatched and brooded that many...but it is honestly really pushing the upper bounds.
Normally, with a larger hen, 20 is the upper limit.
If you've purchased eggs, I always put my focus on those and give them the best chance of success. You don't want to risk purchased chicks for barnyard ones, if that makes a difference to you.
Wait and see what hatches, but I'd leave momma with the ones she's hatched and simply brood the ones in the incubator artificially....if those purchased chicks are a special deal.
Unless the purchased chicks are a really big deal. Then I'd take those and put them in artificial brooding and let momma have all of the barnyard ones....unless you've got an experienced momma and a good grow out set up that prevents stupid chick loss and/or loss from predators and/or loss from foot traffic from the flock or squirmishes therein.
LofMc
EDITED TO ADD: incubator chicks don't always graft easily with momma and the hatched chicks, which is another thing to keep in mind. Being underneath a hen, while hatching, with mum clucking encouragement, begins the bonding between chick and momma. The incubator chicks can be seen as an invader if the hen is not the tolerant type. And/or the incubator chicks often don't see the big dark scary hen as warmth and comfort. So grafting fosters can be a bit tricky depending upon chicks and hen.