Hens are mature female chickens. Chicken refers to any type of domestic fowl that developed from species of jungle fowl. This includes roosters, the mature males, and cockerels, young males. It also includes young females called pullets and castrated males called capons. There are a number of differences between hens and chickens.
Hens are designed to lay eggs while roosters provide sperm to fertilize the eggs. Commercially raised hens lay an average of 265 to 280 eggs per year. The breed of hen determines the egg color. White hens often lay white eggs while brown or black hens lay brown eggs.
Hen Reproductive Tract -- Ovary
The hen reproductive tract consists of the ovary and the oviduct. Usually only the left ovary and oviduct are functional. The ovary is a cluster of developing egg yolks. The ovary of young hens contains 10 of thousands of potential egg yolks.
Hen Reproductive Tract --- Oviduct
The ovary releases the yolk into the oviduct. The oviduct has four major sections. The infundibulum picks up the yolk. If the rooster has mated with the hen, the egg is fertilized at this point. The yolk moves to the magnum where the egg white is added. Then the isthmus adds the shell membranes. The shell gland or uterus adds the shell. It takes 25 to 26 hours to form an egg.
Rooster Reproductive Tract
The reproductive tract of the rooster is much different than the track of the hen. The testes produce the sperm. The testes are located inside the body near the kidneys. Sperm production continues throughout the life of the rooster although roosters often become less fertile with age. The ductus deferens, a small tube, carries the sperm to the outer opening called the cloaca.
Roosters have a larger body size than hens. Rooster combs and wattles are larger than the combs and wattles on hens. Roosters have long, pointed feathers around the neck, shoulder and tail, and hens do not. In breeds with multiple colors, the roosters usually have a greater variety of colors than hens. The spurs on the legs of roosters are larger and more developed than the spurs on hens. By six months of age, roosters crow.
Capons differ greatly from hens. A capon is a castrated male chicken. The testes are surgically removed from the young cockerels. Capons tend to grow more slowly and deposit more fat than roosters. This results in tender and juicy meat.
Young female chickens are pullets. Pullets have not reached sexual maturity and do not produce eggs. Usually pullets begin laying eggs at 18 to 20 weeks. At that point, they are called hens.