This question gets asked at least once a week. The advanced search button on this forum will answer almost any question you could have about quail. Brown (pharaoh) colored coturnix quail often carry a recessive white gene. When you cross A&M (white quail) with pharaohs the resulting offspring will be mixed brown and white. If you took those brown offspring and crossed them with another brown bird of the same genetics, pow, white quail.
Texas quail as you call them are just regular plain old coturnix. People like to think they are different, but a true A&M quail is just a jumbo white coturnix.
