I just candled the duck eggs (day...12? I believe) As of now, there are 8 viable eggs - ALL 8 I can see the itty duck embryo the size of my nail swimming around and blinking its eye at me. Too cool
So far, 8 out of 12 isn't horrible for my first time, and I will be happy with at least a 50% hatch rate.
I threw an egg from on of my white TSC ducks in a few days ago just for the heck of it to see if it was fertile. So far, nothing, but I'm going to keep an eye on the girls to see if they go broody again because she lost her entire clutch of eggs the last round and now that I have an incubator I could help her out a bit.