Chickens would be great farm animals for SHTF if they were not so stupid. The honest truth is they will find a way to get themselves killed.
Build them a nice cage and they will find a way to get out.
They will wander away from the flock and get killed.
They will stay out to dusk, right when coyotes start looking for an easy meal.
They will spill their water.
They will crap in their food and water.
They will crap in laying boxes.
They will roost in high places so if they fall at night they will be hurt.
They will eat stuff that makes them sick – free ranging eating weeds, rocks, pieces of glass, etc.
They will free range out in fields where hawks can see them. They chickens can have all kinds of weeds and cover to forage under. But no, they have to go out in the open away from the flock so a hawk can get them.