Duck eggs... one hard, one soft?

[Nikkimik161]

My Muscovy started laying eggs last week, and they were all coming out with a hard shell. Yesterday I went up, she had laid one hard shell and one soft shell. At least I think it was hers, we only have one egg laying duck and the rest of the flock is chickens. The eggs are about the same size. Is there something missing from her diet? Is it normal for a duck to lay two eggs in one day?

 

[Nikkimik161]

Never mind, a fox got her last night

 

[NanaMarie]

Sorry about your Muscovy I have three along with a few other water fowl and chickens. This could happen with chicken eggs as well. Be sure you are providing calcium. I use oyster shells. I also save my egg shells, boil them and give them back to them.