Interesting Facts About Chicken Eggs

Eggs are amazing things. We often take them for granted, but you won't after you read this article!
By Mrs. Mucket · Feb 22, 2012 · Updated Mar 27, 2012 · ·
  1. Mrs. Mucket
    Have you ever wondered how a hen can lay an egg every day? Why some eggs are brown and some eggs are white? How many days an egg takes to hatch?

    Here are the answers to those questions and many more.

    Hens and eggs
    • Female chickens are called pullets for their first year or until they begin to lay eggs. For most breeds, around 20 weeks is a typical age for the first egg.
    • Some breeds lay eggs daily, some every other day, some once or twice a week.
    • Some individual hens never lay eggs, due to narrow pelvises or other anomalies.
    • Normal laying routines can be interrupted by molting, winter daylight shortage, temperature extremes, illness, poor nutrition, stress, or lack of fresh water. Hens usually return to normal laying habits when the disruption-causing factor ends or is corrected.
    • Most hens are productive layers for two years before declining in production, but some continue to lay eggs for several years.
    • Hens will lay eggs whether or not they’ve ever seen a rooster. Roosters are necessary only for fertilization of eggs.


    Egg development and laying process
    • A female chick is born with thousands of tiny ova, which are undeveloped yolks. Once she reaches maturity, an ovum will be released into a canal called the oviduct and begin its journey of development.
    • At any given time a productive hen will have eggs of several stages within her reproductive system. The eggs most recently discharged from the ovary are just tiny yolks, and the eggs farther down the oviduct are progressively larger and more developed.
    • From the time an ovum leaves the ovary, it takes approximately 25 hours for the egg to reach the vent for laying. During that time period, the yolk will grow larger while being surrounded by albumen (egg white), wrapped in a membrane, and encased in a shell. Pigment is deposited on the shell as the last step of the egg production process.
    • If sperm is present, the yolk will be fertilized before the albumen is deposited.
    • As a chick embryo develops in a fertilized egg, the yolk provides nourishment and the albumen cushions the embryo.
    • Although a hen has only one exterior opening (the cloaca or vent) for egg laying and elimination, eggs are not contaminated during the laying process. Two separate channels, the oviduct and the large intestine, open into the cloaca. As the egg nears the end of the oviduct, the intestinal opening is temporarily blocked off. The egg passes through the cloaca without contact with waste matter.
    • The typical interval between eggs laid is about 25 hours, so a hen that lays an egg every day will lay a bit later each day.
    • Hens don’t usually lay eggs in the dark, so once a hen’s laying cycle reaches dusk time, she will usually not lay till the following morning.
    • Eggshell production drains calcium from the hen’s body. The comb, wattles, legs, and ear lobes will fade as the calcium leaches out. Calcium must be replenished through either feed containing calcium, supplements such as oyster shell, or high amounts of calcium in the soil of birds with outdoor access.


    Egg variations
    • Young pullets often lay malformed eggs before getting established in a normal laying routine. Older hens may occasionally lay abnormal eggs due to age, stress, or illness.
    • Pullet eggs--the first ones produced by each pullet--are smaller than the eggs that the same hen will produce as an older hen.
    • “Fart egg” and “oops egg” are terms for tiny eggs that quickly pass through the oviduct without reaching full size.
    • Shell-less eggs are released before they have time to develop a shell. They may have membrane holding them together or just be loose yolk and white.
    • Double eggs or “egg in an egg” are created when an egg with a shell is encased by the next egg in the oviduct and a shell is produced over the outer egg as well.
    • Double yolkers may have a normal amount of egg white with two or more yolks. In the shell, the egg may be unusually large.
    • Yolkless eggs, also called no-yolkers, dwarf eggs or wind eggs, consist of egg white alone.
    • Occasionally an egg will come out with a wrinkly, misshapen, rough, bumpy, or unusually colored shell.
    • Egg size is dependent on breed, age, and weight of the hen. Larger chicken breeds tend to lay larger eggs; banty breeds lay small eggs. Older hens tend to lay larger eggs than younger hens.
    • The shell color is a breed characteristic. Most chicken breeds lay light-to-medium brown eggs. A few breeds lay white, dark brown, green, blue, or cream colored eggs.
    • Shell color is only “skin deep”-- the eggs inside are the same as eggs of other colors.
    • The shell color intensity of eggs laid by one hen can vary from time to time, with an occasional darker or lighter eggshell.
    • While most eggs have a slight sheen to the shell, some breeds or individual hens tend to lay eggs with a chalkier texture.


    Chicken-and-egg behavior
    • Most hens will lay eggs in the same nest box as flockmates, so it’s not necessary to have a nest box for each hen.
    • Some hens like to lay their eggs in private and others will join their sisters in the nest box. Often two or three hens will crowd into one box while another nest box remains empty.
    • Sometimes a hen will sit on previously laid eggs and add her egg to the clutch. Another might prefer to sit in another area and deposit one egg by itself.
    • Often a hen will sing “the egg song” before or after she lays an egg. Some will sing during the process of laying. It is a cheerful song that seems to be a proud announcement.
    • Chickens learn by example, so a fake or real egg left in a designated nest box may encourage hens to lay there instead of on the floor or outdoors.
    • Unconfined hens may lay eggs anywhere outdoors if they don’t want to return to the nest box. Sometimes a free-ranging hen will go missing and reappear weeks later with a parade of chicks.
    • Chickens like to eat eggs, even their own. An egg that gets accidentally broken will likely be eaten by one of the chickens. If you occasionally find pieces of shell or egg yolk in the nest box, it’s usually nothing to be concerned about.
    • Some chickens become habitual egg-eaters that break eggs open and eat them. An egg-eater should be culled from the flock if you wish to have eggs for the kitchen. Not only will that chicken continue to eat eggs, but others will learn from watching and you may end up with several egg-eaters.
    • Holes in eggs and cracked eggs do not necessarily mean there is an egg-eater in the flock. A hen can accidentally crack an egg in the nest when she sits down or adjusts the nest to lay her own egg. Sometimes curiosity or boredom leads a chicken to peck at an egg without the intention of eating it.
    • Chickens can be fed their own or other eggs either raw or cooked. Eggs provide protein and the calcium in the shell is beneficial for laying hens. A potato masher can be used to break boiled eggs into pieces of egg and shell.
    • Empty eggshells from the kitchen can be fed back to chickens as a calcium supplement without concern for developing egg-eaters. However, to be safe, crushing the shells or running through a blender is a good idea.

    Chicken birds and bees
    • The only reason a rooster would be required with a flock of hens is to fertilize eggs. As a side job, a good rooster also serves as a watchman, warning his hens of predators and other dangers. He also seeks out food for his harem.
    • Even with a virile rooster in residence, not all eggs will be fertile. Some hens just don’t interest a rooster and others never get caught. Often, roosters will have favorite hens that get most of their attention and others remain unnoticed.
    • Hens do not have an estrus cycle. They can mate and develop fertile eggs at any time.
    • Sperm can remain viable in the hen’s oviduct for three to four weeks, so one mating will fertilize numerous eggs.


    Brooding and hatching
    • A broody hen of any breed can be used to hatch eggs and raise chicks from other hens of any breeds.
    • A broody will sit on any eggs, whether or not they are fertile and regardless of who laid them. To gather a suitable clutch of eggs, she will not only lay her own eggs but may roll other hens’ eggs into her nest.
    • While a hen is brooding, you can remove daily any extra eggs she gathers into her clutch. Drawing pencil “equator” lines around the eggs you want her to brood will help with identification.
    • A setting hen will usually leave the nest at least once a day to eat, drink, and defecate. The eggs are not in danger of cooling off too much during a normal foray into the coop or run.
    • Typically, chicken eggs hatch about 21 days from the beginning of incubation or nesting by a broody hen. A few days early or late is not unusual, and some breeds lean toward earlier or later hatches.
    • Not all fertile eggs will develop into embryos. Some never develop due to egg deficiencies or temperature fluctuations.
    • Not all chick embryos will successfully hatch. They can die any time before hatching, even after pipping a hole in the egg. Double yolk eggs rarely hatch due to crowding during embryo development.
    • If a broody hen has pushed an egg out of the nest, she probably knows something is not right with that egg or embryo.


    In the kitchen
    • A normal fresh egg has a yellow yolk, a layer of thick albumen (egg white) surrounding the yolk, and a thinner layer of albumen surrounding that.
    • At opposite sides of the yolk are two chalazae, short white twisted strands of albumen that anchor the yolk to the white. A large chalaza does not indicate embryo development.
    • Every egg yolk has a white disc called a blastoderm. It is usually visible but may be very pale. In an infertile egg, the blastoderm is solid white. In a fertile egg, the disc has a faint or distinct ring that makes it look like a donut or bulls-eye.
    • Fertile eggs are completely edible. In fact, some people consider fertile eggs more nutritious than infertile eggs, but scientific research does not confirm this.
    • Fresh fertile eggs collected daily will not have embryos in them. Embryos do not begin to develop unless the eggs are in a favorable warm environment under a broody hen or in an artificial incubator.
    • The yolk of a chicken egg may be any shade from pale yellow to orange, depending on what the hen has eaten. The color is usually consistent if hens are fed only one type of feed, but foraging hens and those fed kitchen scraps will often produce a variety of yolk colors.
    • The egg yolk or egg white may have red or brown specks in it. These “blood spots” and “meat spots” are harmless bits of tissue and are allowed in commercial Grade B eggs. If they look unappealing, the spots can be removed with a spoon or knife before cooking.
    • An eggshell has a protective coating that prevents bacteria from entering the egg. To retain this coating, eggs should not be washed until just before use.
    • Some eggs are soiled with blood from minor tissue damage or mud or feces from the nest box. This can be wiped off carefully; the shell should be thoroughly dried.
    • If you aren’t sure how old an egg is, you can submerge it in water. The freshest eggs will remain at the bottom of the container, while old eggs will float. Floaters should either be discarded or opened far from your nose.

    That’s about all I know about eggs. Now maybe you can help me answer one more question.

    How can I get my hens to lay golden eggs? Those geese owners have it made.

    Further recommended reading:

    - Chicken Behaviors and Egglaying (Forum section)
    - Cleaning and storing fresh eggs
    - Common egg quality problems
    - Egg Color Chart - Find Out What Egg Color Your Breed Lays

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    Papa John59, 007Sean, terrig and 71 others like this.

Recent User Reviews

  1. 007Sean
    "Good article"
    5/5, 5 out of 5, reviewed May 3, 2019
    Very well written, easy to understand. Great knowledge for the beginner.
  2. jsr5
    "Great information."
    5/5, 5 out of 5, reviewed Apr 27, 2019
    I found this to be quite interesting and informative. Thanks!!
  3. Wi_Pida
    "Very interesting facts!"
    5/5, 5 out of 5, reviewed Mar 29, 2019
    I never thought to even looking into the information you provided. The only thing I looked into "lash eggs", which is an inflammation of the oviduct where the eggs begins its travels. They are not true eggs but may contain bits of egg material and a lot of pus and other material. They are rather disgusting and odd. If you want to see one I've attached a pic.


    1. wrinkled-eggs-web-388x294.jpg


To make a comment simply sign up and become a member!
  1. dutch girl
    Good to know. I am a newbie, lots of good info, thank you
  2. pkincaid
    For a newbie, this was incredibly helpful!
  3. blondiebee181
    Thanks so much! This was great!
  4. Shelby12
    Great:) Very informative, all my questions were answered through this article "Interesting Facts on Chicken Eggs. Thank you as I learnt things i did not know.
  5. garagegirl
    Thank you Mrs.Mucket that was helpful. I guess none of my hens are broody yet because they are only in their boxes to lay the eggs although I have found few on the floor.I will try another way of cooking next time. Thank you have a great day
  6. Mrs. Mucket
    KristinLLB--I'll see if I can add to the article. For now, here's some info: It is not necessary to wash eggs, but I usually do--especially soiled ones and those with debris on them. Eggs have a protective coating that prevents bacteria from entering, and washing can remove that. So I recommend washing just before use. Cold water is said to drive bacteria through the shell, so warm water is best. I either hold under running water or wipe with a damp cloth. Some states require washing before selling.
    Garagegirl--Those are good questions!
    Only a broody hen will sit on eggs to hatch them--if none of your hens are broody, that won't happen. It's best to collect the eggs so they don't get broken. If you do have a broody and you do want her to hatch eggs, you can leave eggs under her and as her sister hens lay more eggs she will pull them under her, too. I like to move the hen to a separate nest when she has the number of eggs I want her to sit on and hatch. An alternative is to mark the keeper eggs and remove all others from the broody hen. I once came home from a trip and found one broody hen overflowing with eggs she couldn't even cover! My helper didn't want to reach under her for eggs so she kept collecting them herself.
    Eggs can go straight to the pan or be stored at room temp or in the fridge. You can wash them as described above.
    Any bird over 16 weeks or so is likely to be too tough for frying or roasting. They are best stewed or slow cooked in water for several hours to tenderize.
  7. garagegirl
    Nice article,but I still have questions? Can I leave the eggs in the boxes and will the hens sit on them to hatch them? If I collect the eggs daily to eat can they go straight to my pan or are there any special things you do before you eat them? Also what is the best way to cook young rooster? We cooked two of ours and they were a little chewy as my 7yr old said. Thanks for your help have a great day.
  8. dutch girl
    Thank for the info, I am a newby so anything helps!
  9. KristinLLB
    that was really fun to read, and really informative! I request a small addition about how to wash eggs in the Kitchen section. I think a lot of newbies would be interested in that.
    Thank you!
  10. Phottoman
    I just wanted to add my thanks too. This was a very well written article, and I even read EVERY comment, and that's rare for me. I bought my first day old chicks eight weeks ago, so I have a L-O-N-G time to wait before getting eggs. But that's OK too since I am the only one in the family that can even eat eggs. And chicken math is happening here too, what started as two chickens is now 22 chickens, but I think I am done buying for a while. I just hope some of mine become broody.
  11. OnTheWing
    Great article - just found it! My pullets have just started laying so this was very informative!
  12. LittleLadyHens
    Thanks for the info! Good stuff.
  13. girls and guineas
    Enjoyed your article, and learned alot! Thanks!!
  14. Genbuddy
    I really enjoyed this article.
  15. Frostymug
    This was very informative. As they say in SW Virginia, 'preciate ya.
  16. mini flock
    Thanks, have learned something new and interesting
  17. kindredspirit
    fantastic article!
  18. Mrs. Mucket
    The only way I know of to encourage a hen to go broody is to start a batch of eggs in the incubator! That has happened to me twice. Seriously though, it's a hormonal thing that just happens. Some breeds tend toward broodiness (for example, Silkies, Brahmas, Orpingtons) and some rarely go broody (like Leghorns).
    My experience is that the ones that do go broody once will do so a few times a year. In my laying flock of eleven hens, there are three dependable broodies, and no one else has shown much interest. If you do see a hen sitting on the nest for several days you can give her some fertile eggs. But a hen can appear to be broody for a couple of days and then leave the nest. The determined ones will sit patiently for weeks.
    Chicks can survive almost anywhere at any time of year if kept warm enough. In a four-season climate, they can be brooded in the dead of winter in an insulated coop with heat lamps. They would need direct heat for the first few weeks, starting around 90 degrees F. and gradually lowering down to the 60s. Some mama hens can do the job quite nicely even in winter.
  19. FowlmouthChick
    Great article for us newbies!!! Very helpful
  20. Dotshines
    good info. Thank you.
  21. Dan A
    Good reading-Thanks!
  22. Babyban
    really good info! thanks
  23. onlyme8
    This is an awesome article! I learned a lot! :)
  24. SydneyLorpa
    Consise, excellent article.
  25. valeriekasnick
    I would like to add a few to my herd of chickens, but how do I get a hen to be broody? My friend has fertile eggs to give me. Also, would chicks survive any time of year in California?
  26. bluewhoo
    EGGcellent article, Thank You!!!!!!
  27. GertrudeLover01
    Thanks!! I needed to know this stuff!
  28. keenecowboy
    Great article!
  29. Mrs. Mucket
    City Lay-Dee: My guess is that a shell-less egg would be fine to eat nutritionally, as it's only missing the shell. But it isn't sanitary, so I wouldn't feed them to people--but I'd give them to my pets since they eat dirt anyway ;)
    gmachicks: My broodies start laying again once they are off the nest. There are some good threads on BYC about how to get them off. I shut them out of the coop during the day and after a few days they'll forget they were broody. Till next time, that is ;)
    Oakieaes: It's a pigment substance that colors the shell, and it varies with different breeds, but I don't know anything more scientific than that!
    royalhighlandbantams: I have had a similar problem with large roosters and I've decided to separate them too. If you can't risk having infertile eggs, I'd suggest a visit every ten days or so just to be sure.
  30. PulletMama
    Many Thanks!
  31. royalhighlandbantams
    I leave my Rooster with my hens all the time and some of them get pretty roughed up. Does the fact that the sperm stays viable for 2 weeks mean that I only have to provide conjugal visits once every 14 days. My hens would sure like having a break and I would provide it, if I could be sure that the eggs would be fertile, since I have a business selling chicks not selling eggs. Can anyone else confirm this?
  32. Helen Carter
    My hens started laying about 2 weeks ago.and your article answered all the questions other people ask me.
  33. Mountaingoat61
    Something I just learned... You can coat eggs with mineral oil and store at cool room temperature for up to 12 months! Make sure the ones you oil have no hairline cracks. The oil seals the shell from oxygen penetrating and spoiling the yolk. This works for store-bought eggs as well. As far as fresh eggs, if you don't wash them they'll last fairly long at room temp due to the coating that they naturally have from the hen. But mineral oil will ensure the long-term storage. If you do store them like this, turn the carton over once a month to rotate the egg yolk. Great for your long-term food storage! :)
  34. elvin
    the silkie pictured looks just like my pedigras! thank you for the comb/ calcium info. i recently had to shut our hens up from predators and their combs were turning pale, so i baked some egg shells for them and the shells were almost instantly devoured! i like to let the chickens roam, but they do just drop their eggs anywhere.
  35. oakieaes
    So what exactly is the dark brown material that makes Copper Maran eggs so dark? I assume it is something different from other brown eggs, since you can wash or scratch if off, unlike with other colored eggs.
  36. DEBRA56
    Very, very good information and Thank You!
  37. SoOregonJoni
    Globalism has killed the goose that laid the golden egg, and 'redistribution of wealth' will insure that it never be revived again. On the bright side, your article is very informative and we can have some peace in raising our own chickens and understanding the egg process! Thank you.
  38. devora
    Nice job. Folks new to BYC should definitely read this before posting egg Qs!
  39. gmachicks
    thanks for the great info. I have 1 question, when a chicken becomes broody and doesn't lay eggs anymore, for over a week, how do you correct that so she will start laying eggs again. I have one that stays in her nest all day
  40. Negui
    So interesting, thank for such great information!
  41. Rev Ross
    Thought I knew it all. Thanks to the "chicks". LOL
  42. Graham Lane
    Even after 10 years of keeping chickens I learned a lot and will be changing my methods! Thanks a lot!
  43. City Lay-Dee
    Great article, cheers mate! Just wondering - do you know if shell-less eggs are ok to eat? When I occasionally get them, I have been giving them to my cat, and he doesn't seem to mind (and he will very quickly turn his nose up at anything he think might be off)...
  44. henry hawke
    Thank you so much for your very imformative article. That explains a lot!
  45. 50sckucky
    Lovemyclucks, sound like your hen might have been egg bound & did an operation on her own behind to get the egg out. She would have probably manage to break the shell herself & then she would have pasted the rest of it, so the next egg, after the egg that blocked her up, would not have been easy to lay with a sore behind, if that makes sense.
  46. Aussie Lady
    Thanks for your valuable information, I learnt quite a bit. I always thought that if you give your chicken the egg shells to eat, they would become "egg eaters" how wrong I was. I will now start collecting these and add this to their feed. I usually give them shell grit.
  47. CoopdeVilleLSR
    Loved this article...thankyou so much!! Do you know how or why the different color eggs...i have often wondered what makes the differences!!
  48. lovemyclucks
    Questing: Do you know if an egg gets bound will the body absorb the calcium of that egg? I have a chicken who had her behind pecked, I don't know if she did it or if the other chickens did but she laid an egg with no shell a couple of days later and sounded like she was going to die in the process. I had her and still do in a cage in the house at night and separated (but together) from the other chickens in the run. Does this make any sense?
  49. 50sckucky
    There is a lot of great information in this article but I would like to add a bit of info I have on the egg shell colour section. The breeds, such as the Araucana, that lay the green/blue egg shells, don't only have that colour on the outside of the egg, but it goes right through to the inside of the egg, so all of the egg shell is green/blue.
  50. Fabidon
    Excellent and quite fascinating! Thank you for sharing your wealth of egg knowledge.

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