I feel an update is necessary on this issue; my first attempt at incubation did not go well.
We started the incubator with 21 eggs arbitrarily chosen (mostly by my almost 4 year old) from all of my hens. I had purchased a Styrofoam incubator from my local Tractor Supply, because the “plans” for the homemade model began to get complicated and were not getting implemented. It is a simple still-air Styrofoam model, and I choose not to pick up any of the extras like the fan or egg turner. We did, however, add a used computer fan to the lid of the incubator, since we have several.
We attempted to candle the eggs, but we were not confident in what we were looking at. In the second week an offensive odor began to emanate from the incubator. Additionally, I was really struggling to keep the temperature in check-it was regularly shooting up to 106 at the lowest setting of the dial.
Our next candling made us much more confident that 9 of the eggs were not developing and may not have ever been fertilized. They were removed and disposed of and most of the smell left with them. That left us with 12 which appeared to be developing.
At day 20 I was hearing peeps in the morning, and by 1:00pm we had a little chick. She was with us for 2 hours and then she laid down and stopped breathing. On day 21 I came home from an errand to find another chick in the incubator. She is now 5 days old, healthy and strong. Unfortunately, none of the other 10 eggs hatched.
What happened? I feel strongly that the computer fan was the wrong choice. We removed that and tested the incubator and it is much improved at keeping a temperature. This is important to me, since my ducks are laying eggs (and making every effort to be certain they are fertilized) but not sitting them. I really enjoy duck, so I want to be able to incubate them. Also, I think I need to place a stronger emphasis on selecting the best eggs to attempt to hatch. With that in mind I plan to segregate one rooster and three hens for my future incubation attempts.
I did a great deal more research, and this past weekend I placed 10 Pekin eggs in new egg turner in my incubator (sans computer fan). I have every hope that I will have a better hatch of ducks than I did of chickens.