Fake eggs in the nest to start, be sure there is plenty of nice thick fluffy bedding in the nest box. If the nest box is open and airy, with interior easily visible, you might need to change that. Are the egg shells nice and strong, or are they (even if only a few of them) on the weak side? A strong shell is not as much of a temptation. It's natural for birds to clean up any weak shelled eggs. Most important, you might need to address diet. What are you feeding? (be sure to include a list of treats) Often the diet is deficient b/c the protein/mineral/vitamin content is deficient, the birds are not getting enough protein, the feed is stale, or the birds are getting too much in the way of scratch grains and other treats. Calcium is IMO a very small part of the egg shell strength equation, as calcium absorption is dependent on other vitamins/minerals. Are you offering extra oyster shell on the side?
