What are the 5 Stages of Chicken Development

Observing the stages of chicken development is a fascinating process. A newly-hatched chick develops into a teenager (pullet or cockerel) and reaches adulthood in around 16 weeks. From fertilization through incubation and hatching, the five stages of chicken development take just under five months. And when a hen has reached maturity, you can expect to get your first egg. 

 stages of chicken development

As any chicken owner knows, raising backyard poultry from chick to hen is a delicate job. For example, the chicken incubation period requires constant temperature, and even a change of one degree can change hatch time by 5 hours. Also, temperature or humidity that is too high or low severely impacts the chances of successful hatching. 

Then when the tiny chick emerges, it only weighs 38 grams (1.34 oz.). That is the same weight as 40 paper clips or eight nickels. However, in no time, the yellow chirping ball of fluff will soon grow into a robust egg-laying hen or shrieking rooster. 

In this article, we will explore the five stages of chicken development. This will give you a fascinating insight into what happens during incubation. You also get great tips on caring for chicks, pullets, and adult hens. 

Why Learn About the Stages of Chicken Development

Understanding the different stages of chicken development is crucial for backyard chicken owners and homesteaders. It allows you to monitor bird health—from hatching through retirement. You can know which type of feed to give them to keep your birds healthy and lay plenty of eggs.

Additionally, understanding what to expect at different development stages helps you anticipate changes in chicken growth. For example, when to increase feed, add supplements to their diet, or resolve unruly behavior in the coop. As chickens progress through the stages of life, being aware of what’s happening can help ensure your flock remains healthy and happy.  

The Importance of Chicken Embryonic Development

Most chicken embryonic development occurs in the egg once it’s hatched. It takes 26 hours for an egg to form, and the hen will lay an egg whether it is fertilized or not. However, if the egg is fertilized, an embryo will start to develop.

According to researchers at Mississippi State University, embryonic development after hatching only takes place if “proper cell environmental conditions are established for incubation to resume.”

Therefore, understanding basic developmental biology is crucial if you plan on incubating hen eggs (or any fowl eggs) in an incubator. It will help you get the right conditions for the embryo to develop and hatch into a furry yellow ball.  

The Five Stages of Chicken Development

Chicken development takes place in the egg when incubating conditions are ideal. After hatching, the chick’s development is relatively rapid. Let’s look in more detail at the five stages of chicken development.

Stage 1 — Egg Fertilization

Egg fertilization takes place when a rooster fertilizes an egg. Like many birds, the rooster performs a courtship dance around his target girl and makes clucking noises. If the hen is receptive, the rooster mounts the hen and transfers sperm without penetration. This happens when the cloacas of the two birds touch. 

Fertile eggs in Nest

So, you are probably thinking—what on earth is a cloaca in chicken language? This is a multi-purpose orifice that chickens have. In hens, they use this passage to poop, lay eggs, and accept the amorous advances of the rooster. In roosters, the two uses of a cloaca are for pooping and transferring sperm.

The “sex” process is swift, only taking around a minute. However, there is only a 15-minute window of opportunity for fertilization to occur. If the sperm doesn’t reach the egg in time, the hen will lay a sterile egg. If fertilization occurs, some cell division takes place before hatching. However, after hatching, incubation only starts under the right conditions. 

Stage 2 — Egg Embryonic Development (Incubation)

A brooding hen will provide the perfect incubation conditions for embryonic egg development to commence. However, if you are hatching chicks without a broody hen, you will need an incubator for embryo development to start. 

The PennState Extension states that four factors are crucial for incubating eggs. These are temperature, humidity, ventilation, and turning. Here is a list of the optimal incubation conditions for chicks to develop in the egg:

  • Temperature—99°F to 100°F
  • Humidity—45 to 70 percent relative humidity depending on the size of air cells
  • Ventilation—Enough ventilation to have 21 percent oxygen (typical household air is sufficient)
  • Turning—Turn eggs three to five times daily from day two through 18
But what happens with chicken egg embryonic development during the first 20 days of incubation? Here is a fascinating insight into what happens inside the egg during incubation: 
  • Day one—The chick embryo and the eyes, head, and nervous system develop. 
  • Day two—The heart and ears form and the heart starts beating by the end of the day.
  • Day three—The nose, wings, and legs begin to develop. 
  • From day four to day 13—The following body parts start developing in this order as the embryo develops:
    • Tongue
    • Reproductive organs
    • Beak
    • Feathers
    • Beak hardens
    • Scales and claws
  • From day 14 to hatching—After the body parts have begun to form, the embryo continues to develop further in this order:
    • The embryo position changes to get ready for “breakout”
    • Beak, scales, and claws become firm
    • The beak turns toward the air cell
    • The Yolk sac enters the body cavity, and the embryo occupies all the space in the egg, apart from the air cell
  • Day 20—The chick breaks through the eggshell and emerges from the egg

According to the journal Frontiers in Physiology, embryonic egg development is crucial in the survival rate of a one-day-old chick. Therefore, the “endocrine system is absolutely necessary for appropriate embryonic development and hatching success.

Stage 3 — Chick Development (Weeks 1 to 4)

Chick Development

Your fluffy yellow balls that have just hatched now need to feed themselves to grow fit and healthy. However, the right conditions are crucial to increase their chance of survival. Therefore, you should place them in a brooder with an appropriate heating lamp. They also need the appropriate feed and water. 

The good news is that a broody hen will teach chicks all they need to know. 

Chicks develop rapidly in the few days and weeks after hatching. At around five days, the first molt of the downy covering starts, and feathers begin to develop. Then after two weeks, its bone development will be more apparent. Then by week three, it should have wings and feathers; after four months, all chicken features and breed characteristics are identifiable. 

Stage 4 — Pullet Development (Teenage Stage Weeks 5 to 15)

Like most teenagers, pullets are gawky with disproportionate features and unsure of their place in the world. During pullet development, the bird’s features begin to broaden, and they gradually start looking like adult chickens.  

pullet development stage

It’s during the pullet development stage that the pecking order begins. This is how chickens naturally organize their hierarchy in the importance of rank. So, you may observe them pushing their chests out, pecking other pullets, and engaging in angry-looking stare-downs. 

Of course, male teenage chickens are called cockerels. But because we mostly talk about egg-laying chickens, we have used the term “pullets” throughout. Usually, between weeks seven and 15, you will start to realize the number of hens and roosters you have.

Stage 5 — Chicken (Adult Stage from week 16)

Chickens become adults when they reach sexual maturity. Many chicken experts say this happens when a hen lays her first egg. However, some people may refer to any hen under 12 months old as a pullet. 

To continue development into adulthood, you should start changing the feed type to a layer feed. This contains less protein but higher calcium levels—essential for good egg-laying qualities. 

Getting your first egg is an exciting time. You can expect three or four eggs weekly from each hen for several years. Although chickens become self-sufficient in scratching for grubs, they need protection and care to stay healthy. 

To ensure a chicken lives for five to eight years, here are a few tips:

  • Raise heritage chickens, not ones specially bred for egg production
  • Clean the coop regularly to reduce the risk of parasites and bacterial infections
  • Get your chickens vaccinated
  • Ensure the coop and chicken run are secure and keep predators out

Stages of Adult Chicken Development

The First Egg

Depending on the breed, chickens begin to lay eggs between four and six months. At the start, egg production may be irregular, and the eggs will be small. But in time, you should start receiving a constant supply of medium to large eggs. As hens age, they start producing fewer eggs until they stop laying altogether—in other words, henopause occurs. 

The First Molt

Adult Chicken Development

Chickens experience their first molt when they are a week old. They lose their soft downy “fur” and start to develop feathers. A second chicken molt occurs during the teenage years when the birds get their ornamental feathers. 

But the first “real” molt takes place around 18 months of age. The molting usually happens in late summer or early fall and lasts eight to 12 weeks. This usually coincides with shorter days. Additionally, the molt can be “soft” or “hard.” During a soft molt, they lose their feathers gradually, and you don’t notice the process. However, hard molting results in losing feathers in large clumps, leaving the chicken to appear ragged or naked. 

During the molting stage, they stop laying eggs. Therefore, increasing protein in their diet is vital to support healthy feather formation. 

Hen Retirement

Hens reach retirement age when they stop laying eggs. After about three years, egg production begins to slow down. Buy this time, your hen—who no doubt has a name and is much loved—has become a friendly companion. But these egg-laying veterans continue to have a place in the flock and help to regulate the pecking order. Therefore, ensuring your “old-timers” are comfortable and well cared for is vital.