Several changes take place during the 18th and 21st days. The abdominal wall surrounds the residual yolk sac on the 19th and 20th days of incubation. The chick draws what remains of the yolk into its body and "takes its lunch with it" (so-to-speak) when it hatches. Thus, the chick really doesn't need to be fed for the first day or two after it hatches.
Fluid decreases in the amnion. The chick's head is under its right wing with the tip of the beak pointed at the air shell. The neck muscle contracts and forces the egg tooth through the air cell, and the chick takes it first breath. This is referred to as internal pipping. At this time, you may hear the chick peeping inside the shell.
On the 21st day, the chick finishes its escape from the shell. The egg tooth makes the initial break in the shell, a sharp, horny structure located near the top of the beak. This is referred to as external pipping.
The hatching process can last for 4 o 12 hours before the chick completely emerges from the shell. As the chick's head rotates from under the wing, the egg tooth pips the shell and continues to break the shell in a nearly perfect circle from the inside until it is able to push the top off the egg.
The chick, as it appears upon freeing itself from the shell, is wet and very tired. For the next several hours it will lie still and rest. A few hours later the chick, now dry and fluffy, will become extremely active and the egg tooth will dry and fall off.
The embryo becomes a chick when it breaks into the air cell and takes its first breath.
After the chick breaks through the inner shell membrane it starts to break through the shell (20th day)
The chick continues to break the shell around the largest point of the egg shell.
Chick almost ready to escape from the shell.
Chick uses its legs and neck to push itself free from the shell.
Shortly after the chick hatches its down well dry and fluff up (the length of time it take the down to dry will depend on the humidity in the chicks environment). The Chick can be removed from the incubator when they are still wet if they are placed in a brooding area at 92 - 95 degrees F .
A successful hatch!
The egg tooth is only present to help the chick break from the egg. Within 12 to 24 hours after the chick hatches the egg tooth will dry and fall off.
Also, if the chicks come from a strain that has the sex-linked genes for feathering rate (very common in commercial strains), you will be able to sex the chicks as you remove them from the incubator. As you can see in the photo of the chick wings above, the male has shorter primary plumes (primary Plumes and covert plumes are the same length). The female on the other hand has primary plumes that are twice as long as the covert plumes. Male carries the slow feathering gene and the female the fast feathering gene.
