In brief, an egg incubator artificially performs the role that a broody hen does in nature.
It is a mechanical device which regulates temperature and humidity at perfect levels therefore creating the ideal conditions which allows the chick to grow inside the fertilised egg, without the hen needing to be present.
In fact, incubators are a lot more successful at hatching eggs than hens. For example, one hen could hatch approximately 20-30 eggs each year but if you use an incubator to hatch the eggs laid by that same hen, you could possibly hatch 200-300 eggs. The reason for this is that a broody hen will stop laying until she has hatched her eggs and reared her young. Plus, a lot of external factors can interrupt the hatching cycle, such as the hen herself getting distracted and allowing the eggs to get cold.
How it works:
Incubators are built to include a motor and a fan which work at keeping the temperature inside at the required level. As the inside temperature of the incubator must be kept at a constant level, ideally the incubator should be kept inside and in a room where the temperature will not drop too low.
The eggs are placed on a tray inside the incubator and they need to be turned at least 3 times a day. The smaller the egg the more will fit on the tray and the larger the egg the lesser will fit.
Water needs be added to the incubator each day to keep the humidity at the correct levels and this level will increase on the last few days of incubation. There is usually a hole at the base of the incubator which allows the water to be added without the need for the incubator to be opened
Both manual and automatic incubators are available. As the eggs need to be turned a couple of times a day the mechanism of the incubator will dictate whether this will be done manually by you or automatically by the incubator itself.
Manual v Automatic
One of the major advantages of an automatic egg incubator is that it turns the eggs for you, so you don’t have to remember to do so each day. The eggs sit in compartments on a specially designed tray. This tray is moved automatically by a motor which cause the eggs to rotate.
If you want to be more involved in the incubation process, then a manual incubator is for you because with a manual egg incubator, you are required to turn the eggs by hand at least 3 times a day. It is best that you mark one side of the egg so that you can track when they were last turned. It is important that eggs are turned regularly as the chick can stick to the inside of the shell.