Oh fascinating! It must be something they are eating then, right?Update: my other ducks now are having odd colored yolks. It is no where near as dark as my Cayuga gal, but they all are a bit different looking. I don't remember this happening last year, but it is possible that the Khaki Campbells were staying closer to the hen house last fall.
That's alarming, but good info to know. Thank you!