Fact Checked

How Exactly do Chickens Lay Eggs?

Michael Pollick
Michael Pollick
Michael Pollick
Michael Pollick

Believe it or not, the egg laying process for a chicken begins in its eye. Chickens lay eggs only after receiving a light cue, either from natural sunlight entering a coop or artificial light illuminating a commercial egg hatchery. The light stimulates a photo-receptive gland near the chicken's eye, which in turn triggers the release of an egg cell from the chicken's ovary.

Most chickens lay eggs on an almost daily basis, unlike some other egg-laying animals which only release an egg every thirty days or so. The chicken also releases a small disk of material which surrounds the egg cell and provides nutrition. The chicken's uterus also fills up with albumen, the viscous substance we know better as egg white.

Chickens lay eggs by receiving light cues.
Chickens lay eggs by receiving light cues.

Meanwhile, a membrane forms around the inside uterine wall, which seals in the egg cell, yolk and albumen. Eventually a mixture of water, salt and calcium surround this membrane and form a thin but structurally sturdy outer shell. This shell is molded in the shape of the uterine wall, thus giving a chicken's egg its distinctive shape. While in the uterus, the egg's narrower end points downward, but it will later turn and be ejected wider end first.

Brown and white chicken eggs.
Brown and white chicken eggs.

Once the egg has fully formed, the chicken's uterus begins to contract in an effort to expel it. The egg moves down a vaginal canal towards an external opening known as a vent. The vent is a common opening for both egg laying and waste elimination, but a chicken cannot perform both functions at the same time. An internal flap known as a cloaca keeps the vaginal canal and the intestinal track separate until either an egg or excrement reach the vent. When a chicken is laying an egg, the cloaca descends and blocks the intestinal track.

Chickens can lay eggs nearly daily.
Chickens can lay eggs nearly daily.

Once the egg passes the cloaca, it is carefully expelled through a series of muscular contractions which essentially turn the vaginal canal and cloaca inside out at one point. Eventually the egg is pushed out through the vent and ideally lands intact on the ground. Many chickens let out an audible cluck at this point, but designated egg layers rarely display any other maternal concern. These chickens lay eggs every 24 to 36 hours at the height of their productive years, so individual eggs rarely attract their attention.

Once a chicken lays a certain number of eggs, it may stop producing more eggs and go into a "brooding" stage, a maternal stage in which the mother will sit on her eggs until they hatch. In order to prevent egg layers from brooding, freshly laid eggs must be removed on a daily basis. Chickens lay eggs as long as they believe they need more to form a proper brood. The egg laying process continues whether or not a rooster provides enough sperm for fertilization. A chicken cannot tell if an individual egg has been successfully fertilized or not.

Michael Pollick
Michael Pollick

A regular AllThingsNature contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

Michael Pollick
Michael Pollick

A regular AllThingsNature contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments


My hen always likes to greet me personally, (I truly think it is her attempt to get the first mealy worms,) but anyway, she got so excited when she saw me coming she ran out of her nesting box and laid her egg on my foot, while leaning against me for her petting. It cracked me up and not the egg.

Eggs are completely clean when they come out. The only reason poop gets on them if is the coop is too dirty or her feet are not clean. Let your chickens walk around in a little pan of water once in a while; they love it.


Thanks for the concise article. Very informative.


I forgot how much light chickens need to lay eggs. Also, usually after 11 or 12, months they will stop laying during molting, when they grow all new feathers, and it usually takes about a month for them to start laying again. After molting they will produce larger eggs, but maybe not every day.


It is really great to read this blog for it has complete ideas and techniques as well as giving helpful images that helped me understand the whole idea of hatching eggs. I wonder if they can give idea also on how to make an incubator. Thanks!


One of my chickens was away from the nest and I notice that she was running toward the nest with her back end kind of in a swat, and out came an egg. She was still running, trying to make it to her nest. So funny


Not so yummy when you actually take the time to think about the origin of the egg - from a chicken's uterus. No thanks!


@anon49031-- I have seen chickens lay eggs closely many times. Not that I enjoy watching them do that, but I have to help my dad with raising chickens at the farm.

Anyway, I don't think it's painful. I don't meant to gross anyone out here, but the way they act while laying the egg is similar to a bowel movement. Just some exertion, the opening expands and whoop, the egg pops out. It's really easier and faster than what people think.

I know some hens make a lot of noise while doing it, but it's not from pain. If the chicken is acting like she's in pain while laying eggs, there might be something else going on.


@anon284874-- I'm not an expert on this but I thought that they can start laying eggs before six months.

How are you keeping your chickens? Are they seeing sunlight? Don't forget they need to see light to lay eggs.

Also, don't be surprised if they just lay one egg per day and if the eggs are very small at first. Younger chickens tend to lay smaller eggs and the eggs will get larger over time. Older chickens will produce less eggs and might even stop laying eggs after a certain age.

They also tend to lay less eggs in winter since the day is shorter and they won't get as much light.


I feel like chickens are being cheated by humans. They go through so much to lay eggs every day and then we just take it and eat it.

Does laying eggs hurt them? It must right? It's like they're giving birth every day. I wonder why they lay eggs so often when other animals don't.


I have a chicken that is losing weight. I purchased her six weeks ago. I have wormed her but I think it's too late. Her crop seems empty all the time. Any ideas, please? The other three girls are fine. --Bob


I have six chickens I bought. I just read they start laying at six months old, and they are almost there. What is my next step to start getting some eggs? Help a poor Oklahoma girl out!


No, a rooster is not needed for an egg to be laid. A chicken will lay eggs regardless. The only reason a rooster would be needed is if one wanted to hatch the eggs (either through a brooding chicken, or an incubator).


Do chickens act different when it's time to start to lay eggs? Do they go off and sit away from the others? --Bob


very interesting stuff. But does anyone know why chicken lay eggs at all?(except for reproductive reasons).


thank you very much, you helped me in my project.


Since there is no umbilical, how do the embryos oxygenate? If they breathe, are they breathing air or liquid? Great article, thanks.


Very informative. Thanks.


Can you please advise if chickens have a uterus?

This article says they do, but others I have read say they don't. Thanks.


My husband told me an egg comes out of the same opening as the feces. I told him no way! I was very surprised and grossed out to learn he was correct. Thanks for the info and ending our argument on this subject.


wow. this was educational and informative enough! thanks so much.


what great info. thanks.


Thanks for the info. you helped me with my science fair project!


Its very informative. I learned something new today about the egg-laying process. it was for our science class. The kids had so many questions about all of this and this article had all the answers thank you.


My chickens just laid there first egg, it sounded very painfull...is it? Even saw some blood on the shell... Great article about the egg cycle and how to keep them laying


it's great! :) Thumbs up!


I had two debates over the "chicken vs the egg". Through this article I was able to get both answers.


good information. i was really curious!


Thanks for the information. regards --keith


Very imformative. Thank you


this is a very interesting article. i want to know further that how do chickens give birth to their child, i mean what is the process of brooding?


could a chicken that has never come in contact with a rooster still lay eggs? and is it pleasure or pain? why do they let out a distinct sound?


Very informative, have been around chickens for years and had no knowledge of the cycle. Thank you for sharing.

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    • Chickens lay eggs by receiving light cues.
      By: andrimka
      Chickens lay eggs by receiving light cues.
    • Brown and white chicken eggs.
      By: aoates
      Brown and white chicken eggs.
    • Chickens can lay eggs nearly daily.
      By: vitals
      Chickens can lay eggs nearly daily.