if theyre nesting you shouldnt see much of them. They usually arent off the nest long, they travel a distance away to defecate (to keep scent down near the nest) then they feed in a bit of a hurry and sneak back to the nest. A hen spending much time feeding likely aint incubating yet. Hens that are still laying leave the nest after tending to things and feed the remainder of the day. The biggest indicator of incubation is ground roosting. When you stop seeing hens roosting in trees, and it may seem like the hens have vanished other than a brief glimpse at one feeding during her "break." I've done incubation at home, and temp and humidity are critical. If she leaves the nest long enough to allow the embryos to cool more than a few degrees for any amount of time, deformities and casualty will occur. I have an electric incubator that regulates temp and humidity, and turns the eggs and a live hen will still have a higher hatch and survivability rate than me, most of the time. They are amazingly critters!
