Like many, I wish all I hunted was wild birds. I try to make several trips each year, just so I can. Every one of these trips requires 10-14 hours of drive time, so I need to schedule a long weekend. I go to Wisconsin for grouse, Missouri for quail, Iowa for pheasant...
I also belong to a "hunt club". You reserve a field and pay for the birds that will be released. No, it is not the same, but all that is available at times. It is legal under the law. I hate to say this, but that is really what it comes down to today. I have a mature pointer who really does not care and a spaniel pup who will learn quicker if there are birds. As my friend, George Hickox says, "95% of the issues with dog training can be solved with 1 word, Birds." (Nope can't keep pigeons here, illegal.)
When I was young, I never had to travel far. It was easy to knock on a few doors. Never had to "scout" for deer. That was simply part of the reason to go out and pick wild mushrooms. Those doors are not closed, they are gone today. They have become strip malls and planned communities.
Revdocdrew is very correct. Whether we own 100,000 of prime pheasant and duck land, make weekend trips, go for long vacations, use state run put & take programs, or have to use a hunt club. It is still better than the alternative, no hunting at all.
The original question was about percentages. Well, my answer depends on the year. Some years 100% wild, some years 100% preserve.
Pete