Mike Rowe caught feral chickens in Miamai Florida on one episode of Dirty Jobs. In the narrative they said they could not eliminate feral those chickens but had a group of people that tried to catch them, I think mostly for fun but also to try to keep the numbers down. I'll include a link to the episode.
https://www.imdb.com/title/tt1581963/
Several years ago, a forum member mentioned a flock that went feral in the Upper Peninsula of Michigan and survived the winter there. They foraged a lot in grain fields that had been harvested and obviously ate snow for water. They survived that winter (they were a standard dual purpose breed but I cannot remember what breed) but his family ate them the following spring.
If you do a search on the internet you'll see that many cities or locations have feral chickens. In the US they are in the south. I did not see any identified in colder snowy places. In general they seemed to need an area with enough people that predators were kept in check but still have green spaces and woodlands where they can forage, nest, and roost. I've seen a few feral flocks in New Orleans but not many.
Growing up in Tennessee Dad had a flock that free ranged. Some slept in trees but most were in a hen house that was locked at night. Those chickens fed themselves throughout the year, but if there was snow on the ground we'd toss them some corn to supplement what they could find. We also had horses and cattle which we fed hay to all winter. That hay was tossed on the ground. The chickens foraged through that in winter so they had a nice supplement to whatever else they could find. We cut holes through the ice on the farm pond for the horses and cattle so the chickens had access to water. The flock was one rooster and 25 to 30 hens. We had plenty of eggs for our use and occasionally some would go to the country store to be traded for groceries. Life was simpler back then, I doubt you could find a store that would accept those eggs today. We ate chicken several times through the year.
The hens hatched and raised replacement chicks. The basic flock were essentially games. I remember Dad bringing home chicks twice, New Hampshire one time and Dominique the other, to bring in new genetics (genetic diversity) and improve size and productivity. I do not consider those chickens to have been feral because they did get predator protection, did get fed during snows, and had some great forage provided in winter.
