Small print inside egg reads: Chick grows as

yolk and albumen are taken in.

YouTube credit goes to Phillip Henley and his daughter Nicole at Emu Logic NSW AU. They produce many worthwhile educational videos.

"Emu In The Sky" - Australian Aboriginal Astronomy

By en:User:Rayd8 - en-wp, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=5444580

(See educational video below from Emu Logic, NSW, AU)