Mr. Cleland, you may well know this, but invasive fire ants are near the top of the problems that bobwhite face. Sure predation takes its toll as does habitat loss/destruction, but the evidence seems to point to fire ants as the leading cause of bobwhite declines throughout its historic range. It's not just the ants eating chicks/eggs, but they are wiping out the local insect populations which chicks desperately need to grow and thrive due to their high protein content. A long range plan that includes control/eradication of fire ant populations may help you attain your goals of having quail return. Some good reading on this can be found below:
http://texnat.tamu.edu/files/2010/09/page23.pdf
AONmagazine.com - Fire Ants Impact On Wildlife - Alabama Outdoor News
https://www.fws.gov/refuge/Attwater_...fire_ants.html
Hope this is helpful and good luck with your efforts!