I would guess the ratio is around 95% public to 5% private.
I actually prefer to hunt public land in most cases, but sometimes it is just not available. Public areas are almost invariably larger in size than private parcels and if I am confined to a small parcel of land, I feel like a caged animal.
As for the difficulty of hunting birds on public as compared to private, there are both easy and hard birds just about anywhere, but on hard-hunted areas, whether public or private, the birds will almost always be harder to kill than on lightly-hunted areas. If I just want to kill a turkey, give me a lightly-hunted private parcel with controlled access any day of the week.