How many chicks can one hen handle?

I have a Columbian Wyandotte who was exhibiting broody behavior repeatedly so we finally decided to just let her have a few eggs. We gave her 5. Over the next couple weeks she convinced the other hens to donate 9 more to her incubating clutch. She successfully hatched out 5 and they looked strong. The rest she gave up on after sitting on them for three extra days after the chicks had hatched. She is being a very attentive mother. Now, we had set up an incubator indoors at roughly the same time and got 13 strong chicks out of that effort. They were only a couple days older than the Wyandotte's chicks. About two days after she started parading her chicks through their run, I decided to experiment and offered her a couple "extra babies" to adopt from the incubator batch. She took charge of them instantly, even showing a bit of aggression toward me (very rare for her) as I set them down, presumably because their pitiful peeping prompted some protective instinct in her. Well, that went so well that we gave her a few more. Same response. Now she has ALL of our hatched chicks in her care and seems to doing well thus far. But I am wondering if this might be too much of a burden on a single hen? How many chicks can one hen handle?

In the TOP image she has ALL of them except the surfer under her plumage.

I once gave a hen 15 incubator chicks. She raised all of them. When I was a kid I remember a hen hiding a nest and showing up with 18 chicks. She hatched and raised all of them. Both these were in the heat of summer. In Maine you are not quite there yet, but unless you get some really cold weather she will probably be OK.

Next time I suggest you gather all you want her to hatch, mark them, and start them all at the same time. Then check under her daily after the others have laid and remove any that don’t belong. As long as you remove them daily you can still use them. That avoids her leaving developing eggs behind. The other potential problem is that if she gets so many she can’t cover them all, some can get pushed out, cool off, and die. It’s really best to start them all at the same time and to check under her daily to remove any new ones.