The Baby Chick - Nature's Miracle Child

The birth of an avian chick is an amazing feat. Unlike mammals whereby the newborn is virtually pushed out into the world and nurtured, a chick has to give birth to itself and then be self-sufficient. Of course, to do that, it needs warmth and moisture which the hen provides, but to actually be born, it must do all the hard work totally by itself. Then, not only must it break free of the egg, it must have certain physiological structures in place for respiration and digestion.

Firstly, let us look at the means by which a chick frees itself from the egg. In order to facilitate hatching, Mother nature has provided the chick with a highly specialised tool with which to break the egg shell. It is a small, pointed attachment on the tip of the upper mandible and is known as a "shell cutter" or "egg tooth". This puts to rest the question of the rarity of hen's teeth, because in reality ALL hens have a tooth (at birth and a few days hence). The chick first breaks into the air sac at the large end of the shell. By raising its the upper mandible, the chick can apply pressure to the shell with its tooth, forcing a crack outwards. This moment is called "pipping". Once this is achieved, the chick rotates itself inside the egg all the while extending the crack in the shell as it goes. Once the chick has turned fully in the egg, and cracked the shell right around (or almost so), it pushes against the shell with its feet forcing the end of the shell away from the remainder with its head and shoulders. Once it has the cap off the shell, the chick pushes itself completely free of the confines of the egg and is born. The tiny shell cutter has served its only purpose and will fall off the beak after a couple of days.

Whilst in the egg, the chick has a self-contained breathing system called the 'allantois". This consists of a fine network of blood vessels within the lining of the egg shell. These are connected to the chick by two arteries and a vein. Once the chick breaks into the air sac before beginning to pip, it begins breathing through its lungs. At this point the chick has two completely separate breathing systems, one within its body and one without. The allantois continues supplying oxygen to the chick right through the hatching process, even though it is now breathing with its lungs. Once the chick separates from the egg, the allantois dries up, breaks free of the chick and

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