[Narrator] But how do the chicks break out
from the cramped confines of the egg?
How can the shell that's
been strong enough
to protect the chick
from the outside world,
be also weak enough to
allow the chick to break it?
The first breath of fresh
air outside the egg.
A captive-bred jungle fowl chick emerges.
It's the climax of the egg's existence.
The shell may look the same
as when the egg was laid,
but out of sight, it's been changing.
It's been getting thinner.
The chick has been absorbing
calcium from the shell
into its own bones, making itself stronger
and the shell weaker.
Not only that, but it also
used the shell's calcium
to create a tool to help it break free:
A hard, jagged tip on the end
of its beak - an egg-tooth
The chick couldn't have
broken free without it.
Even so, it can still take
hours, sometimes days,
to hammer its way out of a shell.
(Latin music)
