Kind of like what happened to the pheasants in PA about 30 years ago.
The small, 60-100 acre farms, many of them owned by guys who'd come back from WWII and used their GI Bill to buy a farm, got sold off when those vets started aging out of farming and their kids either didn't want to farm or couldn't afford to buy them. The ones that didn't get turned into houses, were amalgamated into larger farms or were farmed by tenant farmers. The tenant farmers could only make a go of it by using bigger equipment, which was only productive on larger fields. So, the fence rows - walnut, oak, and similar hardwoods, raspberries, brambles, etc. - got ripped out. The method of farming cornfields changed, too, with stalks being ground and composted after harvesting rather than left standing, eliminating both winter cover and the occasional leftover cob of corn. The fields that were in alfalfa - a big crop in E. Pa. and one where hens would nest and later shelter, feed and fledge their chicks - started getting three cuttings a year instead of two because the farmer needed to make the money from that extra cutting. Moving the first cutting up a week or two wound up taking the tops off of nests because the chicks would still be in the egg. Then, in 1982-1983, there was an avian flu that went through commercial mass henhouses and the wild birds.
The end result was that in the space of 5 years it went from a situation where one could count on kicking out a couple of roosters in every small 5-10 acre field, to one where seeing a rooster was worth writing home about. And it's stayed that way.
The habitat fragmentation from sprawl was the final curtain. Now the only phez you see are plants.
I can't see quail faring any better. In today's America money is the only thing anyone cares about and there's no money in habitat, let alone quail.
