Who’s Egg is this?!

[MamaLynn23]

I have a majority of Production Reds, 3 Barred Rocks, one Speckled Sussex, and some pulleys that I’m pretty sure are still too young to be laying. They are 4 Blue Plymouth Rock and one Golden Star sexlink. I also have three golden Jersey Giant chicks, one Light Brahma chick and one Spitzhauben chick who are all of undetermined sex.
I also have ducks. The hens I have are two Rouen, one Khaki Campbell, one Penkin, and three young Cayuga/probably Pekin mixes (that may be just the age to start laying).
Today I found this olive green egg on the coop floor... almost all my chicken hens lay brown eggs of degrees of brown and the full grown duck hens usually lay white eggs. Would my Cayuga mixes lay something like that?

 

[HappyClucker7]

It does look bigger than a chicken egg, so I would say it's probably one of the ducks that laid it. I don't know anything about duck breeds though, so I can't tell you exactly which one laid it. I'm sure someone else will be able to help more.

 

[citymeetscountry]

Here’s an old post https://www.backyardchickens.com/threads/green-duck-eggs.89051/

I’m thinking it’s your Cayuga mix