Or better land/range management and less fire ants
https://tpwd.texas.gov/publications/pwdpubs/media/pwd_rp_w7000Can't say that can be a problem, but that cycle has gone on since time began, I have seen the same thing when baling hay, almost looks like seagulls behind the tractor for the hawks, but have never seen one get a quail, the quail usually bust out in front of the tractor and fly to a covered edge/fence line.
Where you open minded enough to read the link I posted above? I agree with the premise that land use change, management along with many other natural conditions probably effect quail. Take land management by us out of the equation and you end up with rouge fires cleaning and rejuvenating the landscape, natural rise and fall of predated and predator numbers. Now add the loss of many small farms being worked state wide. Just seems like a bad cocktail for quail from many angles imo.
Around 15 years ago, I hunted a lease in Sterling Co, more blues than I have ever seen and tons of BW, like you said, there where thick pockets of cactus, few trees that where in pockets and this rancher ran cows and sheep, so it had it's fair share of pressure. He rotated religiously tho, supplemented with cotton bales along with tons of oil pads. He also made ground water troughs for birds at all the windmill stations kept full by the overflow tank and cattle troughs. Had awesome deer and some antelope as well, about 40k acres iirc.