I keep seeing this term - seems to imply that it's a necessary step in hatching. I have 11 eggs under a broody hen, who shares space with 3 other hens. Just before hatching I intend to move the family into a separate living area so the chicks can get in and out of the nest in a predator-proof place where they won't be able to sift right through the fence. So what does "lockdown" mean in this case??