Thin shelled eggs?

[headred]

In the last few weeks a few of the duck eggs have been so thin that my finger actually goes thru the shell when I pick them up. Could be just one hen laying them, but does anyone know why the shell would be so thin? Is something missing in their diet possibly?

 

[ChickenToes]

They need more calcium. Add oyster shell or crushed egg shells to their diet.