I have the same thing...I thought it MUST be a snake. I finally figured out those rascals were eating their eggs. I've tried everything suggested, to no avail. But as someone above said, they will eat it ALL with no trace, very fast. I made roll away nest boxes and try to go out early, but I lose any eggs on the ground, unless I get there really early. I figure I lose about 20%. Other than freezer camp, I have no solution, and besides, I am not sure who it is. Very frustrating...