The Complete Life Cycle Of A Chicken Explained

The life cycle of a chicken is quite fascinating for most poultry fanatics!

Just thinking that an egg can hold a tiny germ that in twenty one days can hatch into a beautiful little chick still amazes me.

To think that this chick will grow into a plump hen who in turn will lay eggs to continue the evolution of the flock is a small daily miracle.

If the chick should be a rooster then perhaps one day he will be master of a small flock himself and be charged with taking care of the ladies.

Today’s article will focus on the life cycle of a chicken – all the way from an egg…

Life Cycle Of A Chicken

Life Cycle Of A Chicken:

Stage 1: Egg Fertilization

The first stage of the chicken life cycle is the egg getting fertilized.

Usually roosters will try to court the ladies and put themselves forward as the best rooster for the position of flock husband.

However hens are quite calculating in their selection of a mate.

They consider things like appearance, attentiveness and food finding. All of these things give her some idea of the health of the rooster, his ability to find food and whether or not he will make a good flock leader.

Mating behavior involves rituals such as tidbitting where the rooster will find something interesting and start calling the hens. He will indicate the food by picking it up and dropping it repeatedly until the hen comes to investigate.

The rooster that wins out will usually be the healthiest and best of the bunch.

He will perform the courtship dance to indicate his interest. He will drop one wing to the ground and shuffle around the hen. If she is interested she will squat in submission, if not she will walk away or ignore him.

The mating is a brief and precarious thing.

He will mount the hen from the rear using his beak to hang onto her head or neck feathers and will use his feet and claws to hang onto her.

The hen has squatted in submission and lifts her tail end up to meet him. At this point she will evert her cloaca ready to receive the sperm. The rooster will evert his cloaca allowing his papilla to deposit sperm inside the hen’s body.

All of this takes less than a minute and when they are done she will shake out her feathers and go about her business as usual.

Once the hen and rooster have mated the sperm will begin its long journey to fertilize the egg.

Fertilization occurs in the infundibulum – the part of the reproductive tract that follows on from the ovary. The egg only remains in the infundibulum for around fifteen minutes so it is a small window of opportunity.

If the sperm does not implant itself here the egg will be sterile.

Stage 2: Egg Embryo

This video shows the development of the chick very nicely.

However for those who like a chart to go by one is laid out below – the chart gives the highlights of each day’s development of the chick.

  • Day 1: Development of the germinal disk begins.
  • Day 2: Tissue development starts as does blood circulation.
  • Day 3: Heart starts to beat and blood vessels are visible.
  • Day 4: Amniotic sac starts to develop.
  • Day 5: Elbows and knees develop and their eyes are visible whilst candling.
  • Day 6: Beak starts to form and voluntary movement starts.
  • Day 7: Comb begins to grow.
  • Day 8: Feather follicles start to appear and ear canals open.
  • Day 9: Claws begin to develop and embryo now looks bird-like.
  • Day 10: Egg teeth and claws are formed.
  • Day 11: Tail feathers start growing.
  • Day 12: Feathers starting to appear.
  • Day 13: Leg scales start to appear and they have light covering of feathers over their body.
  • Day 14: Head turns to pipping position.
  • Day 15: Chick will consume egg white.
  • Day 16: They are now completely feathered.
  • Day 17: Egg white is now absorbed and their head is between their legs.
  • Day 18: They are almost fully grown now. Yolk sac still outside the body and their head is under their right wing. If your eggs are in the incubator this is lockdown day.
  • Day 19: Yolk sac moving into the body and embryo now occupies all the space except the air cell.
  • Day 20: The Yolk sac is absorbed and umbilicus now closed. Embryo starts to breathe air and becomes a chick. This is where the pipping starts!
  • Day 21: Also known as hatch day. Hatching is usually accomplished within eighteen hours but can drag on a little.

If your chicks are in the incubator then they can stay there for up to 48 hours after hatching. If you have a broody doing the job she will have them up and moving fairly quickly.

Egg Embryo

Stage 3: Chick

Once the hatched chick is dry and fluffed up they can safely be moved to a brooder area. Once in the brooder the chick should be introduced to water and feed and placed under the light or brooder plate.

The food should contain enough protein, vitamins and minerals for sustained growth over the next several weeks.

These first weeks of life will see an amazing rate of development and growth. Some breeds will grow faster than others. For example Cornish crosses grow so amazingly fast that at 8 weeks or so they weigh a hefty 8-10lbs.

A more sedate growth pace is usual for the average chick. For example a Rhode Island Red chick weighs just over 1oz at three days and by week number six will weigh 1lb.

The chick is initially covered in a fine down coat.

They will start to lose this coat at 6-8 days of age – this first little molt will be finished by week number four.

The second small molt will start around 7-12 weeks. At this point the feathering will start to differentiate the boys from the girls.


Chicks learn things very quickly especially if they are raised by a broody hen. She will teach them all the good things to eat, things to stay away from and dangers to be aware of. A mother hen and her chicks is an endearing sight.

Just remember do not fuss with her chicks – she is in full protective mode and may attack you.

If you are raising chicks without a broody and want them to be friendly with you then talk to them. The more time you spend with them talking and hand feeding the tamer they will become and the easier to handle.

Short trips outside can start as early as 8 weeks or when they are fully feathered out. They should be protected from predators, hot sun, strong winds and drafts. You should watch them closely and if they show any signs of distress they need to go back inside.

Stage 4: Pullet (Teenager)


A chick becomes a pullet or cockerel at four weeks of age and lasts for around 12 weeks.

This can be considered the awkward teenage stage – they look artless, gawky and quite unsure of their place in the world.

It will be during this time that the sexual differences will become apparent in most breeds.

Once you have determined the sexes it is time to separate them. It is also the time that they start to assert themselves and find their place in the pecking order.

The pecking order is a hierarchical system in which chickens self organise themselves into an importance rank.

Every bird knows their place in the flock and birds can move up or down the ladder depending on a variety of things. Such behavior usually consists of pushing, chest bumping, stare downs and pecking – rarely does this behavior result in serious injury.

Once the youngsters are about two thirds the size of the adult chickens you can start the introduction of the new chickens to the older ones. This should be done on a gradual basis in an area that has plenty of room and hiding spaces.

The young chickens will now have to learn their place in a newer and larger pecking order. It may look brutal but try not to interfere unless it becomes a bloody affair.

Cockerels may try to challenge the other roosters but they are usually quickly and firmly put in their place and will remain subordinate until the head rooster starts to fail.

The same will happen with the pullets.

Older and higher ranking hens will ensure that the social order is kept and the pullets will have to work their way up gradually.

Stage 5: Hen (Adult)


Now we come to the final stage of their life cycle.

There is a slight difference of opinion in the poultry world as to the difference between a pullet (teenager) and a hen (adult).

Some people will say that a hen under one year of age is a pullet, whilst others will tell you that once a pullet has laid her first egg she becomes a hen. Regardless of which definition you choose – it all boils down to sexual maturity.

A cockerel becomes a rooster once he reaches sexual maturity.

Hens usually start to lay around the twenty week mark on average. Their first eggs will be small, infrequent and possibly misshapen.

You do not need to worry.

Their egg machinery is new and needs time to get up to production speed. You may need to train the new girls to lay in the nest boxes, but if you have older hens they should just catch on and use the boxes.

During this time pullets should be transitioned over to layer feed somewhere between 16-20 weeks for optimum egg quality.

The layer feed has reduced protein but is higher in calcium and other nutrients to ensure good health and strong egg shells.

It is also wise to offer free choice oyster shell in a separate container for the ladies. Not every hen has the same calcium needs so if they need more they can help themselves.

Chicken Life Span Explained

Ameraucana Hen

While some chicks may die within a few short days of hatching, the majority will survive unless they have something drastically wrong with them. Problems such as genetics, incubator problems or infections can all cause high mortality rates in chicks – while the occasional death is sad it is not cause for alarm.

The biggest dangers to young chicks and pullets is coccidiosis and Marek’s disease.

Both of these diseases have a preventative vaccine available so if you are ordering chickens from a hatchery it is well worth the minor expense.

The average chicken can live anywhere from 3 to 8 years.

Chickens that are well protected from the usual dangers of being a prey animal and other such problems will live much longer lives than they used to. The oldest chicken ever recorded was over 20 years old when she died.

Ensuring your coop and run is safe for your birds will help them to live a long and productive life.

Disease and infection can be problematic especially if the chickens have been on the same ground for a few years.

The build-up of parasites and bacteria can cause many problems from worms to coccidiosis.

It is also worth noting that many of today’s breeds are bred specifically for high egg production.

These breeds tend to die after a couple of years or so because the high rate of production is not healthy for the longevity of the bird.

If you keep dual purpose or heritage chickens you can expect them to live 5+ years.


The life of a chicken is a snapshot of a fairly intelligent and hard-working creature.

These creatures have a structured hierarchy, great memories, are able to learn and give much pleasure to humans.

Chickens of today live much longer lives than the barnyard hen used to.

Back then the average hen would live only for a few years and would lay fewer eggs than they do today. They had to survive on a poor diet gathering what they could from the barn and surrounding areas.

Today’s average backyard chicken by contrast is well fed, produces a huge amount of eggs and in smaller settings lives a very good life…

Chris Lesley Bio Picture
Chris Lesley has been Raising Chickens for over 20 years and is a fourth generation chicken keeper. She can remember being a young child when her grandad first taught her how to hold and care for chickens. She also holds a certificate in Animal Behavior and Welfare and is interested in backyard chicken health and care.

1 Comment

  1. I really learned a lot in this article. Thank you for posting! I’m on my way to knowing more before purchasing and jumping in!

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