https://www.selfsufficientculture.c...gs-are-fertile-or-not-quail-chicken-duck.533/Only thing I can think of is to start incubating a couple and candle them on day 3+. Then you'll be faced with stopping the incubation, or letting it continue to develop. I'm not sure if they get the bullseye on the yolk like chickens do. I've at least not seen it.
I came across this. I'm not sure if it actually works though.