Egg incubation

Egg incubation is the process of keeping fertile eggs at a controlled, steady temperature and humidity long enough for the embryos inside to develop and eventually hatch, which takes about 21 days for standard chicken eggs. It can happen naturally under a broody hen, who manages temperature, humidity, and turning instinctively, or in a mechanical incubator that a keeper has to manage manually or through automated settings.

A machine incubator generally needs to hold temperature around 99.5 degrees Fahrenheit along with a humidity level suited to the stage of incubation, and eggs need to be turned regularly, several times a day, through roughly the first two-thirds of the process to keep the developing embryo from sticking to one side of the shell. Candling partway through lets a keeper check for visible development and remove any egg that is clearly infertile or has stopped developing.

Humidity typically needs to rise in the final days before hatch to help the chick soften the membrane and shell enough to break free on its own. A common mistake is opening the incubator too often to check on eggs, which disrupts temperature and humidity each time, or under-turning eggs during the earlier part of incubation, both of which lower hatch rates even when the equipment itself is working correctly.