Feather sexing as day olds is also a very effective way to determine the sex if you not experienced at vent sexing. I feather & vent sex as day olds and band them then as they grow I get to see how accurate I was. I am getting better now and I think I am close to 80%, Vent sexing is safe and you don't run the risk of killing the chicks unless you have the touch & hands like Godzilla.