Duck egg, hatching and broody duck question

[Duckie doodle]

I have a broody duck that has been sitting on nest for almost a month. She originally layed 13 eggs. I went out to do my normal chores with the ducks and I noticed she only has 5 left. I would like to know how or why she would only have 5 fertile eggs left? I do not see any egg shells laying around. My only thought would be rats. Anyone got any ideas?

 

[Miss Lydia]

Snakes? I’ve had snake in into the coop and scare the hen off her nest and feast on the eggs.

 

[chickens really]

Possibly hidden under bedding.