Newborn chicks (about a day or two old) can be sexed, just like they do at the hatcheries. However, if you're unskilled, you can accidentally suffocate the chick. If you have a firm but delicate hand, Google for the Japanese method of sexing chicks. It involves putting the chick in a specific position in your left hand, massaging its abdomen to make it poop, then using the thumb and index finger from the other hand to firmly press on opposite sides of the vent in order to make the opening protrude slightly. Male chicks' little winkies can be seen; no winky, it's a girl. The organ looks like a tiny black spot, about the size of a pin head.