Yeah, you might be right, byt just to feed the debate I’ll take the defense of the chicken :

• Their sheer number is a big factor : There can be hundreds of thousands in a single farm. Even in tens of thousands die on the first days, the next morning, the survivors will be less fat and more alert
• Red junglefowls are quite adept at living in a rainforest environment despite being nearly flightless and living close to many predators. Their strategy of being diurnal and hiding in the trees at night to avoid mostly nocturnal predators works pretty well and many Amazon predators are noxturnal as well. Mass farm chicken might be too fat at first, but it shouldn’t last too long and feral chicken are known to quickly recover their instincts and start brooding in trees.

-[Tinamus](en.wikipediaorg/wiki/White-throatedₜᵢₙₐₘₒᵤ?wₚᵣₒᵥ₌… while very var from chicken classification-wise (and closer to ostriches), fill a very similar niche and have a similar lifestyle to jungle fowls, also being very poor flyers. This proves that this type of lifestyle can also work in the Amazon. And with tinamu populations being destabilized by deforestation, and chicken being more adapted to a variety of lifestyles, they could outcompete them and steal their niche.

• Just for the scorpion part : Chicken rarely encounrer scorpions due to these being nocturnal. And when they do, it’s a pretty even match : The scorpions might poison them, but the feathers make it harder and the chicken might eat the scorpion first. Source