"Counting grasses and cover objects as a single site each, they've 10 or so spots suitable for laying (though some see little use, and one gets consistent use by a single, determined hen). I've noticed they won't lay in big sheltered areas like the shell of a dog house or under a large leaf of bark, but prefer tight spots with a single entrance. The aviary is about 100 square feet but maybe 2 square ever get used for laying."
So that's why they like the hen caves so much.
"Sharing a nest seems common. Most hens I've ever seen on one nest was three, packed wing-to-wing in a wicker hut. Only one was truly broody, and those two others were the only birds she would tolerate."
It seems like a broody bird is either shy or angry with no in-between. They seem to especially not like the males. Have you ever had one broody quail hand off the nest to another? The red range hen just completely took over from the Italian. I had that happen a lot last year too.