You'll have to forgive me. It has been a while since I took the gamebirds class (oh about 30 years) but as I recall, there is a mineral lacking in the soil that has to do with nesting success in the southeast. Take a look at any range map and see they are generally not found in this area. Yes they can be pen raised but they are not successful in the wild.
Infoman is correct.
"I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes..." (Romans 1:16)