Egg Candling

I have started a 28 day egg incubation project at the Sapphire Elementary School in Monroe, NY. Kindergarten and 1st grade students have been introduced to the life cycle of the chicken and instructed in the care of incubators. Students are monitoring the incubators, checking the temperature and humidity of the incubators and turning the eggs by hand. I prefer to have the students turn the eggs rather than use automatic turners as it provides the children a more hands-on participation in the project.

The second part of my program is to candle the eggs. My purpose in candling the eggs is to show the students the development of the chick embryo and to help them make predictions on how many chicks might hatch in their incubators. Students learn about what characteristics can be seen in the candled egg that shows chick growth. These include the air sac, veins, the eye spot on the embryo and movement. Here is a video of one of the eggs that we candled.




The embryos do not all develop at the same rate. Here is an egg that shows an embryo that is significantly smaller than the one in the first egg. It will be interesting to see if this egg hatches. If it does not, perhaps the slower development of the embryo as seen in the candling may be the cause of the failure.








Some eggs show no development at all. I call these eggs “glowing eggs”. Since there is no embryo or veins inside the egg the candling light passes through unobstructed and the egg appears to glow. I describe it to the children as glowing like an ornament. We compare an egg that glows with an egg that has a developing chick. The students can see the difference and agree that one of the eggs appears to glow much more than the other. Here is a glowing egg.




Most incubation projects call for the removal of eggs showing no chick development. Since I am using the candling observations as a means of gathering data to make a prediction of how many chicks might hatch I leave the “glowing” eggs in the incubator. At the conclusion of hatching students can see how their predictions compare to the hatching results. I have found that leaving the eggs in have not adversely affected the hatching success.

The hatched chicks will remain at the school for about a week so that children can observe their growth. I will pick up the chicks after this period of time and they will live with my flock of chicks, hens and roosters. Next year these chicks will be the hens and roosters that provide me fertile eggs for additional incubation projects.