I’m Scot and new to bluebirding. I have a nest box with 4 eggs. Today is around day 12 of incubation. I found an empty destroyed blue bird egg near my bird bath today, which is a few feet from the nest box. The 4 eggs are still there and the mom is still incubating. There are no other signs of distress or trauma and no baby bird parts anywhere……………just the destroyed egg and yolk.