My wife and I were at the local feed store checking on their new chickens when we were taught a very interesting trick from an old-timer. He says you can hold the chicks up by the scruff of the neck (like you'd hold a baby kitten) and let their feet dangle. He says the males will pull their legs up while the females will always leave their legs dangling. So we put it to the test. They had some chickens already sexed and we started experimenting, and sure enough the males would raise their feet up and the females would keep them dangling down. I had never read about this technique online so I thought I'd share the wisdom. I don't know how old the chickens have to be or if it's only certain breeds but it seemed to work on the 3-6 day old chicks from several different breeds.