My understanding of the chocolate color is that the male needs to have at least 1 chocolate gene and the female cannot have any, then their female babies will be sex-linked (chocolate/brown). I was particularly watching my buff male with my cayuga females out of curiosity, but the 2 chocolate babies I got didn't come out of cayuga eggs, which makes me think that at least 1 of my Silver Appleyard females doesn't carry chocolate genes?!? I could be totally wrong, though! Pretty sure I read about duck genetics on BYC, but it was last year and I didn't save the article.