The way I see it is there is no difference. Birds can fly, but some pen raised ones don't like to. Just ask some pheasant hunters who have hunted pheasant clubs.
I always hear about farmed or high fence ranches spreading disease, but that is one of the reasons for the fences or pens. to keep the wild stock seperated from raised stock. I'm sure in some cases it protects the farmed stock from natural acuring illnesses that affect the wild stock.
Some make it sound like bird farms that raise their game birds to be released or sold to gun clubs to be a non-issue. These birds can fly away and easily breed with wild ones.
My whole point is always the same. Lets not split hairs, we are preditors, we eat meat, we kill animals, fish and birds if we don't want to be hipocrits we shouldn't complain about others that do the same as long as it is done with conservation in mind.
Sorry I just get very tired of double standards. My own teenaged daughter can't stand the thought of me killing a deer and eating it, but loves McDonalds hamburgers. Wow, you know that hurts me! I am the father of a hipocrit.
Mike