A life cycle describes the series of changes an organism undergoes from its beginning to its maturity, where it can reproduce and create a new generation. For the common chicken, this process unfolds through distinct stages, beginning as an egg and progressing to a mature bird capable of continuing the cycle.
From Egg to Embryo
The chicken’s life cycle begins with a fertilized egg. Fertilization occurs internally, about 24 hours before the egg is laid. Once laid, the egg requires specific conditions to develop into an embryo. Optimal incubation involves maintaining a consistent temperature, ideally around 99.5 degrees Fahrenheit (37.5 degrees Celsius). Humidity is also precisely controlled, starting at approximately 50-55% relative humidity for the first 18 days.
Within the egg, the embryo undergoes rapid transformation over 21 days. Cell division begins shortly after fertilization, pausing until proper incubation conditions are met; by day three, the heart starts beating and blood vessels become visible. As development progresses, distinct features like eyes, limbs, and the beak form, along with feather follicles. Around day 18, the embryo positions itself for hatching, with its head typically under the right wing, beak pointed towards the air cell. The yolk sac is gradually absorbed into the chick’s body, providing essential nutrients for its initial days after hatching.
Hatching and the Chick Stage
Hatching concludes the 21-day incubation period. This begins with “internal pipping,” where the chick breaks through the inner membrane into the air cell, taking its first breath. This internal pip stimulates lung function and allows the chick to acclimate to breathing air. The next step is “external pipping,” where the chick uses a specialized projection on its beak, called an egg tooth, to create a small hole in the outer shell.
Following external pipping, the chick engages in “zipping,” rotating inside the shell and pecking a circular line around it, effectively creating a cap. This stage can last several hours, as the chick rests between efforts before pushing and kicking to break free. A newborn chick is wet, covered in soft downy feathers, and has open eyes. Immediately after hatching, chicks require a warm environment, typically around 90-95 degrees Fahrenheit, provided by a brooder, along with fresh water and a specialized chick starter feed; the absorbed yolk can sustain them for up to three days. During the chick stage, which lasts several weeks, rapid growth occurs, and between 3 to 6 weeks, their down feathers are replaced by true adult feathers.
Growth to Adulthood and Reproduction
As chicks mature, they enter a juvenile phase. Female chickens are called pullets, and young males are known as cockerels. This juvenile stage, spanning about 5 to 15 weeks, involves continued growth and the development of gender-specific characteristics, such as larger combs and wattles in cockerels. During this period, their full adult feathering develops, and they begin to establish social hierarchies within the flock.
Chickens reach sexual maturity, typically between 16 and 24 weeks of age. Hens begin laying eggs, with their first eggs often being smaller and less frequent. Roosters reach reproductive capability around 4 to 5 months of age. The typical lifespan of a backyard chicken can range from 6 to 8 years or more, while commercial laying hens are often kept for 1 to 2 years due to economic considerations related to egg production.