If it makes an ear piercing noise - male
If It sounds like I have a cricket in the kitchen - female
(NO, I'm not trying to be sarcastic. With the A&M's, I've yet to find a more efficient method)
that's what I do and it hasn't failed me yet. I brood my chicks inside, and assuming I still have chicks left at 4 weeks, they're all successfully sexed by then.
lol..Thats why i gave up on coturnix...that noise drives me insane to have hundreds cackling all at once!..ruins the beautiful bobwhite calls i love to hear!..