I've given a bit of thought to this.
It seems like whenever I'm hunting and have taken a shot at game, whether it's big game (whitetails) or small game (turkeys, grouse, ducks, geese, rabbits etc.), I find that I have enough adrenaline in my system, from when I first see a potential target to when I pull the trigger, that my ears aren't affected (maybe it's not adrenaline, but something in my body blocks that noise of the gun when I'm focusing on the target and where it lands/runs after I hit it).
The only time I remember when this didn't happen was when I shot a whitetail at about 30 yds with a .308. The deer went down and I was high on adrenaline or whatever it is. The deer dropped in its tracks with a chest cavity shot but when I walked up to it, it was squirming and bleating and making so much noise. I put the muzzle of my rifle about 6" from its neck at the base of the skull and pulled the trigger. That was a bad idea. I could barely hear for about two days. At that point I was cool and calm and sure I had this deer tagged, which I did. I wasn't excited, just trying to end the kill. I still think that one incident affected my hearing even though I've had other hearing damage (tinnitus after shooting and running chainsaws and chippers for a few years).
When bird hunting, If I have to put a bird out of its misery, I just break its neck with my hands...or I'm chasing it down while it's running and I still am full of adrenaline.
If I ever shoot a firearm bigger than .22lr at a range without ear protection, yes I get ringing in my ears, and that's why I wear ear protection then. But I don't while I'm hunting, even if rifle hunting. Seems like my body takes care of itself in hunting situations if I'm smart about it. Keep in mind though that hearing loss in cumulative. Small amounts every once in awhile have the same effect as one "big bang". This is what I've heard, anyway.
And I'm not advocating anything...it's just what I do. It probably is better to wear ear pro. I find that most of my success bird hunting, though, is hearing the birds flush before I see them. I don't have a dog, so I've got to rely on my own senses.