Like ray said she won't start laying on them at all until her nest is complete. Eggs stay dorment until she lays on them as long as the temps don't get to warm and cookor to cold and freeze the eggs and kills them before she starts layin on them. Once she completes her nest she will lay on them all the time and will only leave if something chases her off or it is warm enough during the day that the eggs can stay warm enough without her while she gets a quick bite to eat and a drink. Rarely do they leave the nest for very long if they even everdo. WCL