Quail, pen raised or wild have a very high mortality rate. The biologist say 75-90% perish in their first year.
This will ultimately lead you to the following conclusion. It’s a game of numbers.
If the biologist are right about wild birds, pen raised birds are likely a bit higher especially in the first few weeks. Therefore, if you want to make the turn into spring and your endgame is to have some hens that might have a successful hatch, 1000 birds (late summer early fall release) x .05 (5% survival) = 50 birds into spring / 2 = 25 hens for potential nesting. Figure best case assuming good habitat and weather 5 of those hens set a nest and hatch 15-20 chicks and you come back to maybe 100 new birds that immediately start dying and your 50 bird carryover has probably reduced to 30 birds giving you a peak of 130 birds in August unless the hatch was early and you get a second bite of the apple and some chicks mature and hatch some broods of their own in September ( this how quail can and do at times recover quickly).
You can use this logic to get to your desired outcome but be prepared for complete failure due to weather not cooperating.
On the question of chicks in spring….
Native Americans called spring the starving time and for good reason all of the summer and fall seed have been eaten or covered or rotted, plants are all in vegetative state and bugs are just starting to get moving…So what matters is what you mean by spring…. I’d say early summer is your time slot for this plan… May for me on the Texas coast.
1st of all I like releasing quail as soon as they have fledged into food plots with an abundance of food and cover in 20 bird groups about 1/2 mile apart at least. In fall I work the dogs on them the following mornin so they get some predatory awareness. I may even hit them 2 days in a row, then let them be for a week or 2. I then release 10 more birds in the same places with hopes the newbies get some pretty quick training on predator avoidance, feeding areas, loafing cover etc from the one month veterans and I continue this practice from October to March.
I’ve been trying for about 15 years to establish quail on my little patch of coastal prairie and ag land and have to say it’s been a trial to develop this philosophy and I get a few more birds nesting every year, but I continue stocking in the same manner.
I use about 600-1000 birds per year in this program.
Back to your original question. I like the idea of releasing just fledged ( flying) birds since they aren’t as “pen sour” as older birds that go from the feeder to the heat lamp for 3 months.