And this is all true...
It's a little-known fact that the world's best chicken sexers come almost exclusively from Japan. Poultry owners once had to wait until chicks were five to six weeks old before differentiating male from female (the sex became visible when adult feathers started appearing, on the basis of which cockerels and pullets could easily be distinguished). But for commercial egg producers it's important to identify the females as soon as possible, to avoid unnecessary feeding of unproductive male chicks. Enter the Zen-Nippon Chick Sexing School, which began two-year courses training people to accurately discriminate the sex of day-old chicks on the basis of very subtle cues.