Brandon, quail have 6 different calls. The familiar "bob-white" is a mating call heard only during mating season. If you're lucky, you'll hear quail calling as they come off the roost this time of year....but that's about it. If a covey hasn't been hunted/pressured, you may hear them call 30-35 minutes before sunrise. They'll call for only 2-3 minutes and then that's about it.

The only other call you may hear is the "lost bird" call which is happens with some regularity after the covey has been busted up.

That being said, I have to agree with shorthair, if you're going to hunt quail w/o a dog, you might as well go bust a few clay birds. But, each to his own.