This seems like the right thread to post about a mature (6 years old) and experienced broody (brooded in 2021 and 2023) incubating this time out in the garden 24/7, in a hidden nest. It might be useful for anyone dealing with such a scenario in the future.
I do not know when she started laying this clutch or sitting on them, but I realized I hadn't seen her about much recently on the 27 May; when I found the nest, on the 29th, there were 15 eggs in it, all hers. By 2 June they were reduced to 13; half a shell was visible, spotlessly clean inside, and there was no other trace of it, or the other missing egg, from a superficial look through the perennial plant in which the nest is hidden. I do not disturb her, but do seize the opportunity for a quick look while she is off eating etc. There are predators about and I do not want to draw their attention to the nest's existence.
Which brings us to now, and this morning we are down to 11 eggs; 2 have clearly been crushed, their shells not strong enough for the rigours they have faced over the last couple of days, and their contents are smeared over a number of other eggs in the clutch. The broody is a 'traditionally built' i.e. chunky brick welsummer, with big strong feet, and the contents must have spilled over her legs and brood patch too, but that was not apparent when she came for breakfast this morning. I grabbed a photo and did not intervene. We will see in due course what difference, if any, it makes.
I do not know when she started laying this clutch or sitting on them, but I realized I hadn't seen her about much recently on the 27 May; when I found the nest, on the 29th, there were 15 eggs in it, all hers. By 2 June they were reduced to 13; half a shell was visible, spotlessly clean inside, and there was no other trace of it, or the other missing egg, from a superficial look through the perennial plant in which the nest is hidden. I do not disturb her, but do seize the opportunity for a quick look while she is off eating etc. There are predators about and I do not want to draw their attention to the nest's existence.
Which brings us to now, and this morning we are down to 11 eggs; 2 have clearly been crushed, their shells not strong enough for the rigours they have faced over the last couple of days, and their contents are smeared over a number of other eggs in the clutch. The broody is a 'traditionally built' i.e. chunky brick welsummer, with big strong feet, and the contents must have spilled over her legs and brood patch too, but that was not apparent when she came for breakfast this morning. I grabbed a photo and did not intervene. We will see in due course what difference, if any, it makes.
I wonder if chickens are so clever they really learn from it. Breeding is very hormone driven. 
