Hi, I have herd of people doing this so I tryed it. Maybe I did somthing wrong?? there were 5 eggs total, 2 chicken, 3 duck. the duck eggs were layed within 3 days and the chicken eggs were layed within the same 3 days. There were origanally 5 chicken eggs & she started sitting on them. when she started sitting I switched the chicken eggs for the duck eggs (that I was leaving in a nest hoping somthing would brood them). I wated and wated and finally they started hatching! first one chicken then the next day the other chicken. I kept checking for duck hatchlings but none hatched and the hen finally gave up on them. I broke two of the 3 eggs to see if there was anything in them & if they were developing right. I found one was black & almost ready to hatch (maby another week or less) the other was tiny & white & had several weeks of developing left. The other egg I gave to my one duck that had recently decided to sit & it hatched 2 weeks later. I thought the incubation times were the same for chicken & duck eggs? all of the eggs were the same size & she sat on all of them. They all stayed warm... I dont know what went wrong? Please help.