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The Life Cycle of a Chicken: 4 Stages of Chicken Growth

The Life Cycle of a Chicken

Chickens and humans have a long relationship.

Our history together begins over 10,000 years ago, with the Red Junglefowl of S.E.Asia, and the Grey Junglefowl of India.

Through selective breeding, many new breeds were created, eventually making it to China, where more breeds were created. When the Europeans learned about chickens, they spread them all over the rest of the world.

Today, there are over 500 known breeds of chickens in coops all over the world. It would be hard to imagine a world without chickens nowadays.

A chicken goes through 4 distinct life phases:

  • Embryonic – This stage starts when the egg is laid and lasts for around 22 days if the egg is fertile.
  • Chick – The Chick Stage begins immediately upon hatching, and lasts roughly 65 days.
  • Pullet – This stage is tricky. To all appearances, it is an adult chicken, but still not ready to lay. This is equivalent to the adolescent stage in humans.
  • Adult Phase – The chicken is fully formed, sexually mature, and ready to lay eggs. This stage can last as long as 10 years or more, depending on the breed, and how they are taken care of.
Embyonic Phase
Parts of an egg

Stage 1: Embyonic Phase

Chickens are wonderful, in the fact that they lay eggs for us even when they are not fertile. An egg is a wonderful piece of biological engineering. It has many parts, with each optimized for fetal development. A hen can produce an egg every 25-30 hours.

There are a few parts to an egg, but all you really need to know is the shell, the yolk, and the white, also called the albumen.

The shell contains and protects everything. It is porous so that air and water can pass through it.

The yolk will be the chicken if fertilized.

The white (Albumen) supplies the raw protein and moisture needed to make the required tissues. It also creates a cushion in the event of a mishap.

Ever wonder why an egg is shaped the way it is? It is shaped the way it is so that if it rolls, it will roll in a circle, rather than out of the nest, most of the time…

The Air Pocket is a fascinating structure. Before the chicken’s lungs fully form, the chick gets air through an umbilical cord attached to blood vessels on the inside of the shell membrane.

Before the chicken can hatch, it has to be able to breathe on its own, so when the time is right, the chick will break the membrane separating the air pocket from what’s left of the albumin, and use it as its air supply until it can break through the shell to the outside world. Neat, huh?

What Happens to a Fertile Egg?

An infertile egg never progresses beyond the Embryonic Stage, and will eventually deteriorate if not used. But when fertile, a lot of things happen quickly:

  • Day 1 – Basic tissues begin to form. Mitosis (cell division) has started and the basic layout of the body design will begin to coalesce.
  • Day 2 – The heart will form and begin beating.
  • Day 3 – The tail bud will appear, and the circulatory and lymphatic systems will start to form.
  • Day 4 – The legs and wings start to grow, and the brain and eyes start to form. Lungs and other organs start developing.
  • Day 5 – Joints and cartilage beginning to form.
  • Day 6 – The toes, beak, and claws begin to form.
  • Day 7 – The egg ‘tooth’ (a temporary horn that forms to aid the chick in breaking the shell to escape when the time is right), comb and wattles form.
  • Day 8 – Here come the feathers…
  • Day 9 – The beak splits to become a working mouth
  • Day 10 – Claws become mostly developed.
  • Day 11 – Main feathers form, such as wings and tail groups.
  • Day 12 – Scales form on the feet and legs
  • Day 13 – Eyelids form. At this point, the chick can probably see and hear.
  • Day 14 – The chick turns so that its head is at the large end of the egg.
  • Day 15 – Abdominal organs are shifted to the abdominal area.
  • Day 16 – The chick has its full complement of feathers that it will be born with.
  • Day 17 – The chick’s head will drop down between its legs to make room for the final stage of growth before birth.
  • Day 18 – most of the albumen has been used and the chick just about fills the entire interior of the egg.
  • Day 19 – Almost all of the yolk sac has been used up. The chick can be born anytime now.
  • Day 20 – The chick will begin to chip away at the interior of the shell in an attempt to break through to the outside world. This can take a few days.
  • Day 21 – The chick should break through the shell and enter the world. A chick is born…
Chick Phase

Stage 2: Chick Phase

There are few things cuter than baby chicks. They are like Star Trek tribbles…just little bits of fluff that make little cheeping sounds. They are clumsy, fragile, and just want to be loved.

As soon as the chicks are born, they will emotionally ‘imprint’ on the mother hen. In the absence of a mother hen (such as when incubator-hatched), they will imprint on the first thing they see, which is probably going to be you. Until they reach the pullet stage, around 7 weeks or so, they will be totally dependent on you for everything.

Food, water, emotional support, protection… You’ll have to teach them how to eat, find food, avoid danger, and pretty much everything else.

You’ll need to make a brooder. This can be done with a cardboard box, or even an old plastic pool. The brooder should be inside the coop. Cover the bottom with a thick layer of shavings for insulation. Chicks require a constant temperature of 90⁰F – 95⁰F. A heat lamp and thermometer makes this a lot easier. If the chicks are huddling together, they are probably cold. If they are milling around at the edges, they are probably too hot. They will also require good ventilation.

They will need at least 1 gallon of water in a jar waterer for every 10 chicks, daily. They should be fed starter feed, with at least 15% protein. You can get feed either pre-medicated or non-medicated. The choice is up to you. Premedicated can make it easier to guard against Coccidiosis, a serious parasitical disease, often fatal for your chicks. But if you want to use non-medicated, that’s OK as well. Just be very diligent about cleanliness and sanitation in your brood. Always wash your hands after handling chicks.

Space is very important to the health of your chicks, They need at least 2 square feet per chick.

Their legs will be weak and wobbly at first, but after a few days, they will firm right up. They grow very fast, and you can expect them to double in size in the first 30 days or so.

After about 60 days or so, depending on the breed, they will reach the pullet stage, and things get easier.

It’s OK to let your chicks run free for a bit every day, as long as you watch them closely. After about 2 weeks, they can be allowed to explore their world some.

Pullet Stage

Stage 3: Pullet Stage

Many people skip the chick stage and just buy chickens at the pullet age. They cost more, but they require less care and supervision. But you will miss out on the great time you have with the cute little chicks, and the satisfaction of knowing you raised them from the egg.

For all practical purposes, a pullet looks and mostly acts like an adult bird. They just have not reached sexual maturity, yet. There are some ways to identify a pullet, besides just not laying eggs. A pullet’s legs are more smooth, and better colored than an adult chicken. It’s the same with their combs and wattles. Older birds’ colors tend to fade with age. Pullets are also a bit more trim than older birds.

The young roosters will begin to assert themselves without really knowing why, and the hens will begin to establish their social order, again without really knowing why. Pullets are active and curious, so you may have to keep a close eye on them to prevent misadventures. They will try to see how much they can get away with. Also, in a flock, they are prone to extra bullying. Pullets should be introduced to a new flock as I described in the article, Introducing New Chickens To Your Flock.

The Pullet Stage will last until around 5 weeks. when the hens begin to lay eggs. I know we’d like to see our chickens start laying as soon as possible, but it is better for the chicken and the eggs if you delay this as long as possible, Laying too early can cause lots of health problems with your hen, and reduce the quality of the eggs significantly.

Ever had a store-bought egg with a watery egg white and a pale yellow yolk that breaks if you even look at it too hard? This is from growth hormones, fed to pullets to make them mature faster. It also makes the shells so thin that if a hen tries to set them, they will break. They will break in the carton at the slightest jarring. Take your time with your birds. It’s worth it.

You will need to ease your pullets into adult laying food. Do this by mixing 3 parts starter feed to one part laying feed. As they grow older, you can ease off on the starter feed a little at a time,

until they are around 20 weeks old. Then they will be completely on laying feed and supplements.

Chicken Adult Phase

Stage 4: Adult Phase

It’s been around 20 weeks or so. Our hens have started laying, and the roosters (if we have any) have become very vocal and opinioned. We can feel proud that we have raised our birds to where they can take their rightful place in the world and the flock. They are fully ready and able to supply you with eggs, entertainment, and love.

A word about roosters. When they reach the adult stage, they become very territorial, and very loud, what with all the crowing they will do. Before having any roosters, it is a good idea to check the local regulations first. Some places do not allow roosters due to noise ordinances. You don’t really need a rooster anyway. The hens do fine all on their own.

If you do decide to have a few roosters, only get one rooster for every 25 hens, and make sure they have lots of room to stay away from each other. Rooster fights are vicious and bloody. You can even get hurt trying to break up a fight. Pullet roosters are full of themselves, and will often try to pick fights, so keep that in mind.

When your hens start laying, don’t be alarmed if the first eggs seem small. This is normal, as these are ‘practice’ eggs. After a while, they will start laying full-sized eggs, once they get the hang of it. On average, you can expect 5 or 6 eggs per week, depending on the breed.

They will usually lay for around 8-10 months, then take a break to molt, and have a rest. Chickens may stop laying for lots of reasons, such as stress, not enough light, less than ideal food, inclement weather, etc… It can also be indicative of illness, so you may want to have your chickens checked by a veterinarian if it persists.

Depending on the breed, you can expect your chickens to live anywhere from 5 to over 10 years old. Longevity depends on the breed, health, living conditions, and genetics. For more information on chicken longevity, see the article, How Long Do Chickens Live?

Adult chickens need clean nesting boxes, an adult coop, protection from predators, food supplements and treats, and regular medical maintenance. As long as you are diligent with your birds, you can expect them to stay around as long as possible.

What’s The Oldest Known Chicken

Senior Chickens

I didn’t mention this earlier because it is a depressing subject. No matter how good you take care of your chickens, just like for the rest of us, time will take its toll.

At some point, your hens will slow down on laying, and eventually stop laying completely. They will become less active, and less interested in the social workings of the flock. But their usefulness has not ended. They will still keep the ground loosened up, be useful for bug control, and are still loving.

When chickens reach this stage of their lives, it is a good idea to feed them food supplements, especially extra proteins. Give them plenty of mealworms, and such. And treat them gently. They’ve earned it.

Sometimes, old chickens may go blind, have impaired vision or hearing, and may not be able to walk as well as they used to. You can always keep these chickens in their own runs and coops, for their own protection. They may be bullied by younger flock members. Nature can be cruel to senior members. Just let them finish their lives as comfortably as possible. You owe them that much.

The Bottom Line

Keeping chickens is a great hobby, not too expensive, and is not too difficult to start. The benefits of keeping chickens far outweigh the expenses and efforts you put into them. The main key to success is understanding the different life phases of your birds. Each stage requires a specific range and type of care. With just a little bit of diligence, you can have a happy healthy flock to be proud of.

Knowledge is power. The more you learn about your birds, the more successful you will be. Most flocks fail for one of two reasons. Either the keepers did not take the time to learn about what their birds needed, or they were too inattentive to their needs. Both of these situations are easily avoided.

May your chickens be prolific, and your egg baskets full…

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Carlos Warren

Growing up in Texas, I was fascinated by the world of science and invention, thanks in large part to my father's work at Dow Chemical Company. However, my true passion lay in the natural world, and I became an expert in organic gardening and composting at a young age. I spent hours studying the microbiological communities in our family garden, using a microscope to define the quality of the soil. My love for farming and gardening led me to explore new techniques and methods, constantly pushing the boundaries of what was possible.