Demystifying (but not de-mistyfing) chick incubators.

Believe it or not, incubation isn’t just an invention of the modern era. Historical records show that incubation of eggs was practiced in Ancient Egypt. Mud brick buildings, divided into chambers that were basically large ovens, were heated by burning straw, dung or charcoal. Temperature and ventilation were regulated by opening doors and vents to let smoke out and light in. Humidity was provided by moistened jute placed near and over the eggs. There must have been a lot of guesswork and trial and error involved in a successful hatch, and success rates were hopefully high enough to make the effort worthwhile.

Effortless Modern Incubators

Fortunately, modern incubators take much of the guesswork out of incubation, maintaining consistent temperature and humidity pretty effortlessly, with a little good management. Even the simplest incubators have thermostats, and reservoirs for water. More complex incubator systems have sensors that can register humidity levels and add water accordingly.

Evaporation

We all know that temperature and humidity are critical for a successful incubation and hatch. But did you know that long before that egg you are about to put into your incubator becomes a fluffy, feathered chick, it is still a living, breathing organism?

Cross section illustration of bird embryo inside egg. Getty images.

Pores in the shell allow for the exchange of gases as the embryo develops, and also for the exchange of moisture between the embryo and the air in the incubator itself.

Evaporation is the process by which water changes from a liquid to a gas. Moisture will move from an area of higher concentration, such as the contents of the egg, to an area of lesser concentration, the air surrounding it. Higher temperatures increase the rate at which evaporation occurs. So the comparatively high temperatures in the incubator are a perfect place for evaporation to occur. This is why keeping humidity at the proper level during incubation is so critical, no matter what type of incubator you are using.

The volume of water lost in the egg via evaporation is replaced by air. When the humidity is too high, not enough water can leave the egg. This results in a small air cell (the pocket of air in the large end of the egg). When a chick begins to hatch, he breaks, or ‘internally pips’ through the membranes surrounding him into that air cell, and takes his first real breath there. If the air cell is too small the chick is often unable to pip internally and cannot complete the hatch process. If humidity is too low and too much moisture leaves the egg, this can result in an overly large air cell, and chicks that are weak and adhered to the shell. These chicks often do not survive hatching, and even if they do, they often die shortly after.

Keep It Clean

When the egg is laid, a protective cuticle is created around it. Immediately after being laid, the cuticle is moist, and if it comes in contact with dirt or other contaminants while still moist, those contaminants can be drawn into the egg. Therefore, keeping the nest box clean is of utmost importance when you know you are going to be incubating and hatching eggs. Gather eggs frequently to give fewer opportunities for damage to occur to the egg, and less exposure to bacteria and dirt.

Gentle washing

Gently wipe off eggs if they are a little bit dirty. Don’t submerge them or soak them, but use a damp sponge or cloth. Remember that if you wash the eggs, you are also washing off their protective outer coating, making the shell more permeable. Use water that is warmer than the egg. If the egg is warmer, it will tend to contract as the water cools it which risks drawing contaminants in through the shell.

Solution Cleaning

Use a solution that is specifically formulated for washing eggs, and then be sure to follow the directions exactly. Using too concentrated a solution can hurt the embryos if the solution is drawn into the egg.

Which Incubator is Right for You?

There are two basic types of incubator, forced air and still air. Either one can result in a successful hatch, as long as care is taken to make sure temperature and humidity are consistent. Both are very similar in function and design, with the exception that the forced air incubator has a fan that circulates air over the eggs. For best success, set the forced air incubator thermostat at 99 to 99.5 degrees Fahrenheit and 60% relative humidity. The fan will make sure temperature and humidity are consistent throughout the unit.

A still air incubator can be a little more challenging to manage temperature and humidity, but before the invention of the electronic circuitry and small fans available with a new incubator, countless eggs were successfully hatched in a still air incubator. Set the temperature of a still air incubator to 100-101 degrees F at the height of the eggs. Air will layer, or stratify in a still air incubator, so where the reading is taken is important. Set the humidity slightly higher, 60 to 65% relative humidity during incubation. Check the still air incubator often, eggs can overheat more easily in a still air incubator. Fortunately eggs can handle some variation from the ideal temperature, and tolerate slight underheating better than overheating for more than a few minutes, but the more constant environment you can provide, the better your hatch rate will be.

And, just about any modern incubator beats a brick oven!

This article has been sponsored by Brinsea.