I just had our first duck egg hatch. This egg was 40 days old on the day of hatching. Which begs the question, just what is the incubation period for duck eggs? Is this the normal experience for you? Also, I know some of the eggs I have are no good but what is a good way to tell if they are bad eggs or not? I broke open a couple of rotten ones but then one I was sure was bad was a good one. Bummer.