Life Cycle of A Chicken: Guide on Stages of Chicken Growth

This article explains all about life cycle of a chicken. It includes guide on various stages of chicken growth, average lifespan and FAQs.

Overview on Chicken Reproductive Cycle

The chicken is a fantastic bird with numerous characteristics. Of course, one characteristic that all farm owners could use is laying eggs for human consumption or incubation purposes. 

However, the life cycle is quite exciting and mysterious. A chicken starts its reproductive cycle as an egg. 

In total, a hen will lay hundreds of eggs throughout her lifetime. This usually occurs in the morning or evening when it is not too hot or cold outside, respectively.

The egg that the hen lays fertilize by sperm stored in the infundibulum and magnum. Hen release unfertilized eggs that are infertile and do not complete reproduction process. 

chicken reproductive cycle
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There is no clear explanation as to why the hen releases these eggs, but in most research papers and journals, they do so to maintain a constant level of calcium, which also comes from the large intestines of the hen.

You can read about chicken’s reproductive system in most farming books and zoology  books, but it remains one of the least understood aspects of this fantastic bird. 

It is not uncommon for individuals to have questions in their minds, but it is unlikely that they will ask them for fear of being thought weird or stupid. 

The most important aspect of the reproductive system is the ability of the female/hen to lay eggs. If an individual cannot reproduce this behavior, there is no point in keeping chickens.

Hormones regulate the primary stages of the chicken reproductive cycle. These hormones peak and drop at certain times, and these times can be predicted with some accuracy. 

As a result, farmers and owners will get the best eggs possible from their chickens. This article will give a brief overview of the life cycle of the chicken so that you can understand this fantastic bird better.

Also read: How Many Eggs Does A Chicken Lay A Day?

Complete Life Cycle of a Chicken: 5 Stages of Chicken Growth

Chickens go through a complete life cycle from birth to death. This includes five well-defined stages of development. Each stage is determine by age, appearance, or other factors. 

Every chicken keeper needs to understand the different stages of a chick as it will help take care and make sure chickens are comfortable at all times.

The five stages of a chicken life cycle are:

Stage 1. Egg Fertilization Stage

rooster and hen mating picture
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Rooster and Hen Mating Results in Egg Fertilization

After mating, the egg of the chicken is fertilized and becomes an egg.

The following is how this process works:

1) First, sperm cells move up to the surface of the uterus through small tubes that are only for this purpose. These sperm cells will wait here until they’re needed to fertilize an egg.

2) Next, the rooster mounts the hen and clasps her abdomen with his legs. This causes their cloacas to touch each other because that is where they excrete waste.

3) Then, sperm cells get released from this region into the v@gina of the hen through another opening known as the cloacal kiss.

4) The sperm cells make their way to the infundibulum (the funnel-shaped opening of the oviduct), where they wait for ovulation.

5) Then, the egg travels down to this region through the oviduct. The vaginal plug leftover from when it entered swells up around the infundibulum, trapping the sperm cells to allow fertilization.

6) After the egg is fully formed, it travels along until it reaches the uterus and attaches itself to a piece known as the shell gland. This is where the egg white fluid gets coated onto the outside of this membrane to protect its contents from being damaged.

7) Then, the egg is passed through the vagina and out of the hen’s body during a process known as ‘laying.’

In addition to this, fertilized eggs progress in their development much faster than unfertilized ones. This is because they have a constant supply of nutrients from the yolk provided to them through the albumen. 

As for unfertilized eggs, they don’t have this benefit and instead still progress at the same rate as normal unfertilized eggs do.

Also read: Complete difference between rooster and hen

Stage 2. Egg Embryo Phase: Life Cycle of Chicken Eggs

chicken embroyo development in grwoth period
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Day 1: The first day of incubation is the only time that the egg is both fertilized and incubated. This single-cell embryo consumes food stored in its yolk to fuel cellular division.

Day 2: Cellular doubling proceeds rapidly as the cells eagerly absorb their yolk’s nutrients, thus tripling in number by Day 2. The small cluster of cells begins differentiation.

Day 3: With the cells subdividing, they become tightly packed, each surrounded by its yolk-sac wall. The embryo is now called a morula (mulberry).

Day 4: The cells have differentiated into two distinct but densely packed groups by Day 4 after fertilization. This process of differentiation is called compaction. Soon, the embryo will take a recognizable shape as an early gastrula with an enlarged blastopore that deepens to become the yolk-sac (vitelline membrane) and amnion.

Day 5: On Day 5, the embryo is still a blastula with an inner and outer layer of cells. This group of cells has yet to establish any particular orientation, but they are beginning to take on specific identities by now. The cells of the future head region are becoming more elongated.

Day 6: By Day 6, the embryo is a hollow ball of cells with a large blastopore opening to the yolk-sac. The vitelline membrane separates the yolk from this cavity and its developing gut. Cells of the future head region migrate inward toward another cluster of cells on the future chest region.

Day 7: By Day 7, the embryo is a gastrula with two very distinct layers of cells. By now, the future head region has established its top orientation and looks like an embryonic head rather than just an enlarged yolk-sac.

Day 8: By Day 8, the embryo is a mid gastrula with the embryo in the vertical orientation so that it now has a future tail region. The cells on either side of the blastopore are beginning to change shape and move inward to meet in the midline.

Day 9: By Day 9, the embryo is big enough to develop the early body axes. The embryo’s future back (dorsal) surface faces either left or right depending upon which side was against the wall of the yolk-sac at fertilization.

Day 10: By Day 10, the cells on either side of the blastopore have moved inward and come together to form an archenteron (primitive gut cavity). The cells here will become endoderm. Cells destined to become the heart are now in their final positions on either side of the archenteron, beginning to beat.

Day 11: By Day 11, the embryo is a classic gastrula with three distinct germinal layers: ectoderm, mesoderm, and endoderm. Embryo circulation is functional as early as Day 10 as blood vessels begin to form in the embryo.

Day 12: By Day 12, the embryo has formed somites (the blocks of cells that will make up muscles and bones).

Day 13: By Day 13, the embryo has grown in size six to eight times its original length at fertilization. The amniotic fluid that protects and cushions the embryo fills more than half of the volume occupied by the embryo. Small air bubbles are trapped within this fluid early in development, which can be seen on prenatal ultrasound as early as 14 days.

Day 14: By Day 14, the embryo has grown much larger than at fertilization, measuring about 1/2 inch long by 1/4 inch wide. The amniotic fluid, which protects and cushions the embryo, is now two-thirds of the volume occupied by the embryo.

Day 15: By Day 15, the embryo is approximately 0.4 inches long by 0.2 inches wide, with a distinct head region forming at one end of the body that now measures about 1/6 inch to 1/8 inch long. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon). The neural tube has closed at the level of the future fourth somite.

Day 16: By Day 16, the embryo is approximately 0.6 inches long by 0.3 inches wide, with a distinct head region forming at one end of the body that now measures about 1/4 inch to 1/5 inch long. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

Day 17: By Day 17, the embryo is approximately 0.8 inches long by 0.4 inches wide, with a distinct head region forming at one end of the body that now measures about 3/8 inch to 1/2 inch long. The chicken brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

Day 18: By Day 18, the embryo is approximately 1 inch long by 0.5 inches wide, with a distinct head region forming at one end of the body and a tailbud at the other, which now measures about 5/8 inch to 3/4 inch long. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

Day 19: By Day 19, the embryo is approximately 1.2 inches long by 0.6 inches wide, with a distinct head region forming at one end of the body and a tailbud at the other that now measures about 3/4 inch to 7/8 inch long. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

Day 20: By Day 20, the embryo is approximately 1.4 inches long by 0.7 inches wide, with a distinct head region forming at one end of the body and a tailbud at the other that now measures about 7/8 inch to just over 1 inch long. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

Day 21: By Day 21, the embryo is 1 to 1.4 inches long and 0.8 to 0.9 inches wide, with a distinct head region forming at one end and a tailbud at the other that now measures about 1 inch long or more. The brain is divided into the forebrain (telencephalon) and midbrain (mesencephalon).

The first sign of bone tissue is seen in cells migrating from the neural crest that form ear bones. This is the last day during which it can hatch on its own without help. 

If no hatching has happened by now, there’s only one option left- removing the egg from incubation (so that bacteria doesn’t start growing inside), cleaning out the embryo, and putting it back, hoping it’ll hatch on its own.

Also read: Best incubator for chicken, duck, quail eggs

baby chick vs pullet vs adult hen in life of a chicken
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Stage 3. Baby Chicks: Life Cycle of Chicken Kids

After 21 days, the embryo develops into a chick with visible head and neck structures, eyes, and beak forming within the eggshell. It is important to note that this stage can last for about six weeks or more, depending on the breed of the chicken. 

During this time, it is also crucial for a chick to be in a warm environment with the recommended temperature of about 37.5°C or 99.5°F.

Stage 4. Pullet: Life Cycle of Teenage Chicken

A pullet is a young female chicken that is between egg-laying age and sexual maturity. A hen typically becomes sexually mature at about 20 weeks of age, which means it has begun its second phase of life (first laying eggs) but is still considered a baby. 

The average weight for this phase is 4 pounds to 6 pounds. This phase can last from 16 to 22 weeks, depending on if the chicken is a layer or a grower.

Stage 5. Hen: Adult Chicken Life Cycle

Chickens at this stage are fully grown and will be productive if used as layers or for meat. This is also when chickens start to molt (lose their feathers), during which all new feathers grow in, replacing all the old feathers. 

This stage can last for about one year up to five years, depending on how well they are taken care of and the breed itself.

How Long Do Chickens Live? Average Lifespan of Chickens

The average age of chickens is about six years. All domesticated chickens are descended from the red jungle fowl, which only live for 4-5 years on average. 

However, they can live up to 15 years in some instances. The record for most extended living chicken was 22 years old.

Growing Period: On average, baby chicks take about 21 days to hatch. Once hatched, baby chicks go through a rapid growth period where they gain weight quickly. It is not uncommon for chickens to double their birth weight in about six weeks.

Feathers and Plumage: The feathers start growing when the bird is around three months old, but it takes another six months for its plumage to develop fully. This is so because feathers and wings grow much more slowly than other body parts.

All chickens have the same type of feather: a stiff bristle that repels water and insulates them from extreme temperatures.

Breast Bone: At nine months, the bone structure begins to harden during the second phase of their growth period. At this point, you can feel their breastbone, and they can no longer effectively brood.

Feather Position: Around the 12th month, the feathers will move to where they should be in relation to their wings. For example, chickens with eight primary wing feathers usually get them at about one year old. Also, around this time, roosters will grow spurs if they have not already.

Mating: Roosters start crowing as early as five or six months old, but hens won’t start laying eggs until around 18-20 weeks of age. If a hen has been mated too young, she may stop laying for a couple of months.

Egg Laying: Chickens begin to lay eggs when they are about six months old. If you have a hen that is not laying, she may be going through a reproductive pause due to molting. Molting usually takes about one month per year and can affect egg production.

Thinning Down: Chickens naturally lose some of the weight they gained in the six weeks after they hatch. They lose between 10-15 percent of their body weight. They lose between 10-15 percent of their body weight. If they do not, then it may be an indication of illness.

Death: Chickens usually die from either predation or disease. Stressed birds are more prone to succumbing to disease than healthy ones, so keep them calm and stress-free if you want them to live long lives!!

In conclusion, chickens go through rapid growth and development during the first year and then slow down and gain more slowly after that. This is the reason for the different ages at which roosters can be used in cockfights or meat.


The life cycle is around 7-8 years long, but there are many stages of development throughout its life. First, it starts as an egg, hatches into a chick, then becomes a baby before it reaches maturity at one year old. 

Then the chicken will live for another 5-7 years to full adulthood. Poultry also has an average of 2-5 chicks every year.Age, weight, and height are some of the factors that affect how fast a chicken grows. 

This is because age determines how long it goes through each growth stage, weight affects what type of feed it needs to maintain its current state and status, and height shows how much space it needs to move around comfortably. 

Many factors can affect a chicken’s life, but it can work around them if it has enough room and access to food and water at all times.

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