We had several get away from us while training dogs about 25 years ago . It was in an area that had no birds . When finished training there were several birds left so we set out a covey set up for the puppies . Long story short they joined the others . Today there are several coveys there with at least 25 + birds in each . The man that ownes it said he fed them for the winter so he knew they lasted to summer . He feels the birds he sees now came from those that got away . Since there were few birds in the area it would seem he was correct.