I agree. There are other rational considerations; they know there is food close by. They watch me cook so they know.They're very confident! If I were a chicken, I'd lay my eggs in such a nestbox because it's so safe.
There is also water at hand. What I think but cannot prove is the hens that sit here hatch chicks. I think this is something they take into account. If this is true then they know which hens have sat here and produced chicks, so there is some level of planning and risk assessment involved. What may also contribute is either 4 days before hatch, or shortly after I move mum and chicks into one of the maternity units. They must be aware of this. After all, one day there is a hen with chicks in the house nest box and the next they've all moved.Consider though, whether or not the hen is thinking about this when she lays that first egg here. Then consider that the pullets from the tribe who haven't seen a hatching hen in the nest will also try to lay their eggs here. That's a lot of planning!
It is also possible that the roosters encouragement to lay here, rather than elsewhere has most influence. You're left then with trying to work out why the roosters think this is a good nest site. I mean they don't sit here. They don't have direct experience of sitting and hatching here. They do come by and check on the hens but once they're installed the roosters even if they visit don't pay much attention to the sitting hen.
It gets more complicated. The roosters and hens pick their nest sites together in the cases I've seen. With the pullets, who haven't laid an egg they will tour prospective sites, sometimes a week or more before the pullet lays an egg. One or the other, or both must know the egg cycle is due to start.
It's fine with me to talk about it all you want here. There were many times I lived across the country from family members when they passed and was unable to get there for a variety of reasons. It is just the most helpless thing. Just when you really need to be with your family you can't get there. So I hope you see us as your second family and can feel the hugs across these miles.
I put a bowl in the pullets' run and the bachelor pad too. Eventually, Lucy got brave enough to taste it, and before I was finished with my chore and coming in the hens had eaten all of there. I gave them 4 little bowls since three are 7 hens in there (probably a cup total). The pullets and cockerels are pretty sure it's poisonous.