That's what is happening on my Rouen's nest. My white ducks and her are starting to take turns. I have only had the white ones for about 3 weeks today is the first day I seen them sitting and wow are they (the white ducks) protective. One is standing guard then they switch the only one not sitting is the male I have never seen this and am truly interested, I am not disturbing but observing. Should I start counting 28 days from today?