I would be interested in knowing how many quail you have now and how many in a year or two after your habitat changes. I personally would have a hard time taking out the thick areas scattered across the fields. Seems to me this is a good way to move around the field and still have escape cover nearby. As far as hawks are concerned the coopers is the biggest bird predator. They do not need big trees to perch from to hunt, they will use fence post or any old bush. A very stealthy hunter and if prey is around they will hunt them; big tree or not. Red tailed hawks and hawks of this type is often seen perching in trees. This type of hawk is not a great threat to quail because they are much slower and have a wide range of prey, where as cooper hawks are nearly 100 percent bird eaters. Biologist are like DR.s they don't always make the right diagnosis.