posted 2 weeks ago
I'd be more willing to try this with seeds than eggs in my ecosystem. I expect this would be much harder to do in my cool climate.
Also, saving a single egg has the downside of chick being totally imprinted on the human and won't know how to interact with fellow chickens. This is already an issue with incubator chicks hatched as a group, but at least they have fellow chicks around even if not adult chicken input.
Also, if the goal is to have a back-up to your incubator, I suspect having a back-up heat source like a fire, which can bring a pan of water up to 100F or so, would be more helpful. Incubators come in different sizes and shapes, but the larger the pot of water, and the smaller a space you can create around the incubator, the better the odds of the eggs surviving a long power outage.
Last but not least, that single chick will need heat even after hatch. Joel Salatin I recall uses heat from decomposition to keep chicks warm, but he's normally raising a large group and "huddle heat" is a thing supporting the decomposition warmth.
I admit I'm totally biased to getting a mother hen to do the job if at all possible! If I want more chicks than the hen can reliably set, I've put eggs in the incubator and under mom at the same time, then in the dark, when the chicks have hatched, we add the extras to the nest, and so far, it's worked out well.