How Does a Chicken Hatch Out of Its Shell?

After 17 days of incubation beneath the mother hen, the chicks will start to peep. The mother hen can hear this sound and will begin to get more attentive toward her eggs. She will stop turning them, something she has done several times a day since the brood began. She will also begin to peck holes in the rounded ends of the shells to let more air in for the babies to breathe while they are hatching.

By the 21st day, the eggs are already beginning to hatch. The chicks use their egg teeth (small, sharp points on the tip of the baby's beak that break off after hatching) to break a larger hole in the shell. The baby ratchets his body around the interior of the shell until he has completed a full circle of peck marks. After that he pushes on the pecked area for hours until he has completely broken free.

Moisture levels must be checked regularly. This is true with the heat levels as well. Too far below or above 100 degrees, growth will slow and the chick will become deformed and eventually die. Humidity above or below 55 percent will cause harm to the chick as well. Each egg must be rotated at least three times a day, but preferably more often. Rotations stop on the 17th day, as they are no longer needed to prevent chick death.

In an incubator the chicks start the first hole in the shell with their egg teeth, and then complete the rotations that make the holes larger. After that, they push upward until the shells give way. The newly hatched chicks will be tired from their exertions and will likely not need to eat right away. Supply food as soon as possible, however, just in case. By the third day after hatching, the chicks should be eating.