Feral chicken are known in several places. They can be pretty successful and have been signaled as threats to ecosystems and crops in archipelagos like Hawaii and Bermuda. But I’ve thinking about Brasil: Given the sheer amount of chicken being bread there, the presence of the Amazon rainforest, which has a similar climate to whence jungle fowls, the chicken’s ancestors come; and its already fragilized ecosystem, isn’t there a specific risk there ? So far, I’ve seen no South American country listed as famous for feral chicken presence . But hypothetically, if a few millions of fowls escaped a massive Brasilian farm and swarmed the Amazon; what could happen ? Would they quickly die off, due to having lost adaptations to wildlife, having an insufficient ratio of roosters and facing many predators ? Would they outcompete one or two local bird species and steal their niche, but otherwise fit fine in the food chain without further disrupting the ecosystem? Or would it spell a great ecological catastrophy ?
That’s only a concern for one generation tho, which afaik for commercially bred chickens might be just a matter of weeks
Chicken eggs take 21 days to hatch, so 3 weeks, and then to adult size it probably 6 weeks minimum, so I’d say 2 months minimum they need to survive as a collective.