The hatchery people have professional chicken sexers that check their vents. Even the best sexer can mix up sometimes because their are so many slight nuances to their parts so hatcheries are only about 90-95% accurate. Sex link breeds you can sex by birth because a male is one color and a female is another (example a boy is black while a hen is red). There are different ways to breed sex-linked chickens but I really don't know much about it. Wyandottes are sadly not sex linked so it's a waiting/ guessing game. I have gotten pretty good at sexing but I still have to wait until they are 2 weeks old at the least to make a guess. If only it was easy as sexing a dog! lol
Ok, thank you that's what I was trying to figure out! How they knew my girls are girls
