I found this one in the barn pen that leads out to the aviary this morning. This is the first egg to come out of that pen and they weren't separated yet. The birds that are in the aviary are: Wood duck pair (bonded) 2 mandarin pairs (onepair is for sure bonded, one so so) and another mandarin male Runner pair 4 call ducks and 4 call drakes My first guess was that this was a call egg - it looks just like one to me - BUT those calls never ever go into the barn pen. There is a pophole that leads in there and they have never once been through that pophole that I know of. ALl the wild ducks frequent the barn pen though. There was no nest, which led me to believe that the runner could be responsible, but it does not look like a runner egg to me - all my other runners lay green eggs, and bigger. My best guess is wood duck. Any other guessers?