I think the eggs will develop if fertile. A hen can spend up to two weeks gathering the clutch, during the process she will spend some time on the nest but usually returns to the flock each day/evening and roosts with the flock until she has enough eggs in her 'clutch' to satisfy her.... at that time she will begin setting and this is when most folks think a hen has 'gone missing'.We lock our hens up. Every evening they take themselves in to. The coop, however we noticed one was missing so we searched all over and nothing, we were worried as there has been possums hanging round lately so we do doing 2 hour possum searches lol, the next day about 12 she appeared from nowhere, so we decided to keep them in there coop for a day, I let them out yesterday and he never returned again so again I went looking finding her sitting on over 20 eggs....... My question is will the eggs still hatch I left her there and she is still there this morning
The eggs will begin developing after they are all brought up to a particular temp for an extended period of time. Interruption on the first day of that incubation probably didn't kill them, though if some were genetically weak or vulnerable it may have. I would allow her to sit on as many as you think she can handle, then candle on day 7-10 and remove any clears. If they are all clear at that time you can get her new fertile eggs. Just make sure you know of a source of eggs before the candling so you aren't caught unprepared if you need to replace her clutch. If it is only going to take you a day to get new eggs she can remain on the duds till you have the replacements for her.