I have 4 half Cayuga half Rouen ducks and none of them lay a dark egg. I had one light gray one once... none since... jealous...I think one of my black runners laid her first egg today, because it is a dark grey color. None of my chocolate runners every laid this color before. Is it normal for a black runner to lay this color, or does it mean she has a bit of Cayuga somewhere on her genetic line?