In 40 years of releasing game birds my personal experience is that you lose 85-90% of them in the first 3 to 4 weeks.
That's with commercially raised birds (battery brooders with wire floors and large flight pens)
They don't know how to survive, no fear of predators.
However I have had great success with using game hens as surrogate mother's.
They can usually incubate a dozen eggs and have 90 -100% fertility rates.
As long as they have suitable cover and feed to free range they do well.
The adolescent birds have a survival rate of around 80%.
Obviously this isn't practical for large scale operations but for a hobbiest with a couple hens it can work.
Last time I did this one hen nested in an overgrown corner of my garden and hatched/reared 10 Hungarian partridge

Imo the best chance at pen raised bird survival is being released where there are wild birds already established. We do 20 place roosters on Tgiving morning and everybody gets to shoot without blasting the natives into extinction. Believe it’s been going on 7-8 years now, so circa 150 roosters have been released on 25 acres. There’s been solid wild birds there before and after. Out of the 20 placed I think the most ever killed was 12 in a morning. Food for thought all puns intended.

Ok . So at one time I was told "stocked" or "pen raised " quail or pheasants if they survive until the following year will not nest, because the don't have "nesting' instincts. Or "mothering" capability's. Have always been intrigued about this. What say you the trapperman group?? As a counterpoint, Was told domestic chickens have been raised for centuries and they still get "broody." G.

Economics

I have "Surrogated" thousands upon thousands of bobwhite quail. Herd quality varies widely between operators. We had some that would survive til the next summer. One year out of many we had an incredible survival rate and pairs everywhere. They had no idea where to nest. We found several on 2 tracks. We had exactly one brood hatch and we watched that brood slowly dwindle from 10 or 12 to 2 birds by the end of summer. We haven't tried johnny houses but are considering it. I have heard wild stories but have never witnessed it myself. We have several acres of excellent quail habitat and our wild population fluctuates between 3 or 4 covies to around a dozen. It seems to depend upon how the rain comes during nesting time. Pesticide applied liberally to soybeans and corn guarantees a low population of quail.

Great picture Lugnut. I had our one year old black lab Sam out for his first time hunting and it's been a blast. I never trained a bird dog, but Sam seems to have already figured out his job and he loves it. My 12 year old son is also learning. We have been practicing shooting clays and he's ready to carry a gun next time we go out.

As for the stocked birds...there's a hawk on every pole when the stocking truck comes. Just too many predators of all sort.

Endangered species act changed the way birds of prey
were handled.

While a Boy Scout I helped stock birds.
M to F was 50-50. No hens shot.

I stocked heavy near our place and would feed them like chickens.
Many would hold over and I never saw young ones.

The birds raised by small hobby guys held over better than the large growers.
Still no reproduction.

Try raising free range birds of any kind and watch what kills them.
It is not a secret.