A few preliminary notes: I opened up a post the other day about a 'failed hatch' but was rather surprised to find it was about 2-3 individual eggs (out of 20+) that failed to hatch, this was not a failed hatch but rather a normal, successful hatch with a couple duds. If you've ever incubated eggs or are thinking about it, a certain percentage of loss, death, and failure is a routine part of the business, just like planting seeds or buying bananas, you're going to have an occasional bad one. So what is normal? What is a failed hatch? What did I do to ruin my eggs? That last one is not even a question you should ask! Really think about it for a minute, how much actual control do you have over the development process and hatching success? Besides for providing the proper conditions, you have 0 influence on whether that egg will hatch or not. Yes, you can ruin your hatch by messing up the temp in the incubator but you can't make those same eggs hatch if there are underlying issues even if you provide a perfectly calibrated hatching environment. So don't freak out, give up, beat yourself up, or anything else over a failed hatch, rather learn from it! We can't change whether that egg will hatch or not, all we can do is our best to maintain the proper conditions to bring it about. Basically, select eggs with a great chance of hatching (fertile source flock with good nutrition and genetics), maintain the egg properly preincubation (temperature and time), incubate that egg in a timely fashion, have a reliable incubator with external thermometers to make sure temp is stable, make sure the eggs are turned properly, and candle the eggs to watch development, removing any duds. But don't just toss those duds, rather open them up and see what stage they are at and learn from them. They can actually tell you something and improve future hatches! The following is by no means a complete and exhaustive list of all the issues at each stage, but rather the most common ones. You'll also notice shipped eggs are on every single list. While they can be a great way to expand your flock or get access to otherwise inaccessible species or genetics, they also are a gamble. You can see issues at every stage of development, so don't freak out or try and figure out what you did wrong when the post office did it for you! Saddled or moving air cells mean your eggs were traumatized during shipment, they can still hatch but expect significantly reduced hatch rates! Humidity is also rarely mentioned as a major issue, it is important to maintain proper levels for your species but it also doesn't appear to tank your hatch rates like a wonky temp or cold/heat stress pre incubation. The data here was compiled via trial and error and close observation along with the personal experience of many a would-be hatcher, it is not scientifically tested or peer reviewed. The most interesting thing I observed in torturing my hatching eggs was that cold or heat exposed eggs, 2 week old eggs, and even shipped eggs usually developed just fine through the first half of incubation but usually died during the second half, indicating that the genetic material of the pre incubated egg was damaged and while it could still develop into an early embryo it couldn't become a healthy chick. So take care of those pre-incubated eggs and make sure your incubator runs at a steady and proper temp and you're over halfway to hatching success! But when your hatch rate isn't a happy one, here might be a few ideas why:
