Large commercial poultry hatcheries employ chick sexers to distinguish male and female baby chicks prior to shipping large chick batches to local feed stores and pet stores. Chicks also must be sexed in order to ship females to egg production factories and males to the butcher. Many hobby farmers desire the ability to sex their own baby chicks in order to keep egg layers or make sure they don't have more then one rooster at a time. Chick sexing is not an easy task and takes a great deal of practice. Even professional chick sexers are only accurate 75 percent of the time.
Turn the baby chick upside down when it is one day old. Hold the chick's entire body in the palm of the hand with the head facing your chest and gently squeeze its body using all fingers to hold firmly. With your free hand, exert firm pressure on either side of the vent in an almost rolling action, taking care not to damage the chick or break its delicate bones. The chick might expel a little bit of fecal matter through its vent. Look at the vent closely and watch for a tiny bump that resembles a pimple. This is the male. If the chick lacks this bump, it is a female. Bump sizes can vary dramatically, but female chicks should have no bump.
Study sex-linked color traits in the breed of chickens that will produce the chicks. Several breeds produce chicks whose initial feathering will help identify their gender. Barred hens who have black and white striped feathers can be mated with non-barred roosters who do not have this feather pattern. Together they will produce chicks that sport the opposite color patterns of the parents. They will have only barred male chicks and non-barred female chicks. Unfortunately, only a few breeds of chickens can be sexed in this way.
Monitor the chicks as they grow. Male chicks will gradually begin to exhibit rooster characteristics. The chirp will deepen and turn into more of crow than a chirp and sound a bit like the chick is being strangled as it struggles to use its new voice.
Look closely at the feathers that begin to replace the chicks' downy fuzz. The males' feathers will be more narrow and less round. They will glisten more when held before the light. The feathers on the male chick's neck and back will be pointed while those of the female will be oval in shape.
Watch the chicks' heads as the combs begin to develop. Male roosters will be the first to develop combs. Combs usually begin to develop at around four weeks.
Look on the feet of the chickens for spur development when they are four weeks old. Roosters have sharp toenails that are called spurs. These form off the back of the ankle. Hens lack sharp spurs.
Evaluate growth at four to five weeks old. Most male chicks will be slightly larger then female chicks.