How do you tell boy and girl chickens apart when they are adults?

You can determine the gender of chicks two ways. Depending on the breed of chicken it is, you can look at the pinfeathers. Males usually have longer pinfeathers than females do. You can also look at their vent. In order to determine the gender a chick by observing their vent, the feces must be literally squeezed out which opens the rectum, or cloaca. Males have a bump that appears at the opening of the cloaca. Females sometimes also have a bump, but it is always smaller and less defined.

Vent sexing or identifying the sex of a day old chick by looking at its sexual organs is done by very few, very well trained people. It takes a long time to learn how to identify the more than 15 different shapes.

Feather sexing is based on feather characteristics that differ between male and female chicks.The feather appearances are determined by specially selected genetic traits that must be present in the chick strain. Most breeds of chickens do not have these feather sexing characteristics and the feathering of both sexes appear identical.

The easiest method of sexing chickens by the novice small flock owner is to care for the birds until they begin showing the natural secondary characteristics of their sex. In males, the combs and wattles will become larger than those on females and the head will become more angular and masculine looking. The female will remain smaller than the male and is more refined or feminine looking.