Found this near when I dumped the bedding from the kennel my Bumblefoot Queen's kennel yesterday. The other ducks had been in the area as well. I didn't get an egg from Mildred yesterday, so very well could be from her, but it is perfectly round and very rough shell. Shell is very hard, not soft at all. Have been given them oyster shell. Should I be worried? It was outside on the ground, so it's possible it is from someone else (another bird), but I would doubt it.