Cats in the wild won’t hunt anything too large, but they do like chunky animals that have as much meat as they can hunt. Rabbits are one of the biggest animals they hunt. In areas that have rabbits, its usually their main source of food. Any small game that size or smaller is a target though, including birds.

Duck, Turkey, cow, pig, deer, and bison all are not on the table for a cat to hunt. Cats will only scavenge if they are starving and otherwise will prefer to hunt for their food.

Your vague belief that it might be possible a cat stumbles upon a bison that just has died of natural causes does not make standard cat food natural or inline with the cats personal choices.