How the Chick Emerges from the Shell
The time of hatching is an important event in the life of the chick. The head of the chick develops at the large end of the egg.
Between the 15th and 16th days, the chick orients itself so that its head is near the air cell at the large end of the egg. Several changes, preparatory to hatching, take place between the 17th and 19th days. Fluid decreases in the amnion. The neck acquires a double bend so that the beak is under the right wing and toward the air chamber. The remaining yolk sac is retracted into the body cavity for use as food after hatching.
On the twentieth day, the chick moves his head and the beak pierces the membranes and enters the air cell. The chick slowly begins to breathe the contained air and it may be heard to peep within the shell. Using its egg tooth (a tiny, sharp horny projections on the end of its beak), the chick pecks at the shell thousands of times. After the chick has made a hole in the shell, it stops pipping for three to eight hours and rests. During this time, it is acclimating its lungs to the outside atmosphere.
During the process of hatching, the shell will be shipped while the chick turns in a circular path. In two to five hours, the chick has made about three quarters of a turn inside the egg. As the chick progresses in its movement around the shell, it begins pushing on the egg cap (large end).
Squirming and struggling, the chick works feverishly for about 40 minutes pushing at the cap. Finally, with a vigorous twist of the neck, the chick breaks free from the shell, still wet and panting.
At first, the chick is wet and seems exhausted. However, in a few hours the chick is dry and fluffy and wanders about the new and mysterious world. The yolk inside the chick will help supply its food and water it needs for the first 24 hours while it remains in the incubator, before moving to the brooder