Sexing chicks is instinct as much as it is science. Professional hatcheries have someone on staff to accomplish this task -- for the backyard chicken enthusiast, it's a matter of trial and error, often with emphasis on the latter. If you've ordered large numbers of female chicks from a hatchery, you've likely received one or two that grew up to be Henries rather than Henriettas, because even the pros make mistakes.
Professionals sex chicks by holding a bird upside down and examining its vent. They look for evidence of a developing male sex organ. The Mississippi State University Extension Service website states that, while the "copulatory organ" can identify a bird as male or female according to shape, more than 15 different shapes exist to identify. You can learn to do this, but it takes a lot of time, and an inexperienced sexer's initial accuracy rate might not be any greater than 60 percent or so.
In some breeds, reliably sexing chicks is easy because of differences in feather colors. While color sexing is common in commercial laying breeds such as the Rhode Island Red, it's not available in the heritage or ornamental breeds often found in the backyard flock. In color-sexed breeds, the male chicks are usually lighter and females darker. Some breeds carry genes that promote certain color patterns in males and others in females. With exception of the rare mutation, sexing by color is an accurate means of sexing specific breeds.
In most breeds of chickens, the feathering of males and females are identical. Some breeds, though, do have different feather shapes according to sex; if you're raising chicks of such breeds, gender determination is simple. The barred Plymouth Rock is one breed that you can sex according to feathering. Depending on breed, males' feathers grow more slowly; those who feather more quickly are females.
Secondary Sex Characteristics
If you have backyard chicks, you might have to wait a while until the secondary sex characteristics kick in before you can tell the difference between the girls and the boys. Depending on the breed of chicken, that's between the ages of 4 weeks and 6 weeks. You will notice a particularly masculine or feminine appearance in the individual birds, with the pullets smaller than the cockerels. The latter's wattles and combs soon become larger than those of the pullets. Males also start trying to crow.
- Mississippi State University: Sexing of Day-Old Chicks
- The Atlantic: The Joy of Sexing
- Mother Earth News: Sexing Day-Old Chicks -- How to Identify Pullets and Cockerels
- The Poultry Site: Sexing Chicks in the Backyard Flock
- Queensland Department of Agriculture, Fisheries and Forestry: Chicken Sexing
- University of Kentucky Cooperative Extension Service: Sexing Day-Old Chicks
- David De Lossy/Photodisc/Getty Images