When a hen reaches eighteen to twenty weeks of age, she begins to lay eggs. Generally, a hen will lay one egg a day. In a natural environment, the hen will continue to lay eggs in her nest until she has several there. She then sits on the eggs until they hatch.
A hen’s reproductive cycle generally lasts twenty-four hours during the summer months. Her cycle is set by day length. As the days shorten, and winter approaches, a hen will lay fewer eggs, skipping some days. Some hens stop laying eggs all together until the spring arrives. The reason behind this is that winter is a bad time to raise chicks. The cold weather decreases a chicks chance of survival.
Hens, like all other birds, deposit eggs through the same opening they use for waste removal. Because of a flap of skin that stretches down, eggs are not contaminated by any waste materials that may be near the opening. A hen does not need to be fertilized to lay an egg. Most hens in a laying facility have never even
been in contact with a rooster.
After the hen lays an egg, she will leave the nest. The egg will quickly cool enough to keep an embryo viable for up to two weeks. Every day, the hen will lay another egg until she has several in her nest. She then becomes “broody.” A broody hen will sit on her nest all day and night, her wings spread slightly to help keep the eggs warm. Because the embryos’ growth was paused while the nest was being laid, they will all develop at the same time.
A broody hen will leave her eggs, briefly, once a day to defecate, eat, and drink. Anyone who gets too close to her eggs will be pecked at. After three weeks of brooding, her chicks will hatch. Any eggs that don’t hatch will be left behind as she brings the new chicks out into the world for the first time. The nest will be abandoned.
In farms or egg-laying facilities, this natural process is broken up. Lights can make the hen think that the day length hasn’t changed, resulting in a more consistent number of eggs. After an egg is laid, it is removed. The hen thinks that there is still not enough eggs in her nest, and will continue laying. A hen that is resistant to laying in a nest can be encouraged by placing a few fake eggs into her nest. Hens will continue to lay eggs until they reach two or three years of age.
Besides daylight and old age, there are several other reasons why a hen may stop laying. One is due to poor nutrition. A hen that is not receiving proper amounts of feed will be unable to produce eggs. Another reason is molting. After several months of egg laying, a hen may go through a molting cycle. Due to the energy required to molt, a hen’s body will not have the energy to produce eggs. Hens may also stop laying temporarily due to stress or disease.
During the course of their lifetime, a hen may lay as much as thirty times her body weight in eggs. At one egg a day, for almost two and a half years, that is about nine hundred eggs. For a little chicken, that is quite an accomplishment.