Definitely. If what he has is contagious, you don't want to expose her any more than you have to.
I hope he gets better too. Make sure he stays warm. I'd bring him inside to make sure he's eating and drinking as well as staying warm. You will also be able to see what his poop is like and...
If you have other quail, make sure that you separate this one from them. Even if it has already been separated, keep a close eye on your other birds for symptoms. If your bird doesn't make it, you might consider sending the body to a lab for a necropsy. The tests aren't too expensive, and it...