This study of blue (scaled) quail decline, conducted by the Caesar Kleberg Institute, finds that brush removal, monocultures of non-native grasses and cattle removal cause blue quail numbers to fall.
The prescriptions would seem obvious: graze cattle in ways that help plants, preserve brush, and get lots of weeds growing alongside your grass.
Equally obvious (but contrary to what is promoted by Big Wildlife): Avoid poisons like glyphosate (Roundup) and tibuthurion (Spike). These kill everything mentioned above, everything else, and over time build up residues in soil and water. This ‘bio-accumulation’ wreaks havoc on the micro-organic life on which the health of all plants, animals and habitat depend.