We usually think that the chick breaks his egg shell, freeing itself from its hot and suffocating prison directly into the gentle cool morning breeze, using only its beak. This is not true.
I think I want to go back…!
A number of things happen as hatching time draws near. As the eggs develop, water escapes through the shell in the form of water vapor. This water loss creates an air space at the broad end of the egg, where the chick is able to take its first breaths. The shell also becomes thinner as calcium from the egg shell is incorporated into the skeleton of the chick as it develops.
They don't really use the beak to break the shell. A few days prior to hatching, the chick will develop an egg tooth, a small sharp calcium bump on the top of its beak.
The egg tooth is a tiny structure that helps the chick break through the last barrier that separates them from the cruel world.
Notice the egg tooth on the tip of this killdeer chick’s beak. Usually, the egg tooth falls just after the first pecks.
They can even use the beak in part of the process, but in the first few pecks it would be impossible, since the chick is curled up inside the egg:
As the chick uses its egg tooth, in conjunction with a special hatching muscle at the back of its head, it begins chipping away at the egg, creating a small hole, called a “pip.”
The pip creates a continuous supply of air as the process of hatching begins. From within the egg, the chick will begin scratching the shell in a circular path around the large end of the egg, weakening the shell. The chick is then able to burst the egg open.
I got it, Mom!
Interestingly, both the egg tooth and hatching muscle are also present in reptiles.
You can see an adorable baby chick hatching in the video below:
So cute…