Roosters, the male members of the chicken species, do not lay eggs; this biological function is exclusive to the female hen. Egg production is the result of a specialized reproductive process that only the female avian anatomy is equipped to perform.
Why Only Hens Lay Eggs
Egg production relies on a specialized female reproductive tract that roosters lack. The hen possesses a functional ovary, which releases the ovum (yolk), and a long, complex oviduct. The rooster’s reproductive system, centered on two internal testes, is designed solely for the production of sperm and male hormones.
The oviduct is a single, elongated tube where the egg is formed around the yolk. As the yolk travels through, layers of albumen, shell membranes, and the hard shell are progressively added over about 25 hours. The hormone estradiol-17β, a type of estrogen produced by the hen’s ovary, stimulates the development of the oviduct and coordinates the entire egg-formation process. The rooster’s anatomy simply does not contain the structures, nor does it produce the necessary high levels of female hormones, to initiate or complete this complex biological process.
How to Identify a Rooster
Telling a rooster from a hen becomes straightforward as the birds mature, usually by four to six months of age. Roosters develop larger and more vibrant combs and wattles, the fleshy red structures on the head and under the chin. Testosterone, the primary male sex hormone produced in the testes, drives these characteristic developments.
Distinctive feather shapes also serve as reliable markers for identification. Roosters develop long, narrow, and pointed feathers around the neck (hackle feathers) and lower back (saddle feathers). The rooster’s tail is often adorned with long, curved sickle feathers, which are not present on a hen. Many roosters also develop bony, defensive spurs on the back of their legs.
The Rooster’s Purpose
While roosters do not lay eggs, they serve an important purpose in a flock. Their primary biological function is to fertilize the eggs laid by the hens, making it possible for chicks to hatch. Hens will lay eggs regardless of a rooster’s presence, but those eggs will be infertile and incapable of developing into an embryo.
A rooster’s presence also contributes to the safety and order of the flock. They act as vigilant protectors, watching for predators and sounding an alarm call to warn the hens of danger. By establishing and maintaining a social hierarchy, roosters help reduce fighting and bullying among the hens.