I've noticed that my chickens prefer to lay their eggs next to another egg. They don't seem to care which box or whether it's a real egg or a dummy in the nest. I have four nest boxes and two dummy eggs that I've been moving around. It's hilarious because wherever the dummy eggs are is where the real eggs will be. I often find that they've all laid in the same nest and I can manipulate which one by where I place the dummy eggs.