"Hawks are more of a problem on quail than anything else." Yes, they are. Really tall grass does provide a lot of protection from hawks.

Armadillos, possums and coons tear up the nests. Ravens kill quail, especially pen raised quail. On our place we have coveys of naturally wild quail as well as pen raisedquail from wild parents. We do shoot every possum,
coon, raven and armadillo we see. Have killed about 30 coyotes on the place since 2001. Actually it is rare to see a coyote track there now.