Yes, chickens will eat each other. Note these birds were under no duress… they just chose to go for the higher quality protein that was available.
One thing about self-reliance is you’ll get into reality in a way you never have before.
It’s mostly good though.
If you want to grow your own food easily (so you don’t have to go cannibal) check out https://backyardfoodproduction.com
Homesteading Basics: Cannibalistic Chickens