“How can the shell that’s been strong enough to protect the chick from the outside world,” Sir David Attenborough asks, “be also weak enough to allow the chick to break it?”
This clip from The Egg: Life’s Perfect Invention explains how this jungle fowl chick absorbs calcium into its bones from the egg’s shell, weakening the egg and strengthening the chick. It also has a hard spot at the end of its beak called an egg-tooth, an essential tool for hatching.
Jungle fowl are colorful birds found in Asia. From Britannica:
The red jungle fowl (G. gallus) is the ancestor of the domestic fowl… The gray jungle fowl (G. sonnerati), of southern India, may also have contributed to the ancestry of the domestic fowl, which in some breeds shows a similar grayish and white pattern. Other species inhabit parts of India and are found also in Sri Lanka (Ceylon), Java, and some Indonesian islands.