This is on display in Hawaii on the island of Kauai. The Polynesians brought their chickens thousands of years ago. Those chickens escaped into the wild, but produced few eggs. Americans brought their domestic chickens that produce lots of eggs and kept them in chicken coops. After a hurricane in the 80's researchers noticed a spike in the number of feral chickens on the island. The two breeds of chickens have become one and they are everywhere. Kauai is the only Hawaiian island that doesn't any predators for the chickens. You'll see roosters at 5000 feet above sea level and down by the beach.