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

    Share This Article

    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. todasaves14
    Very good reading.
  2. francel
    Good article !
  3. HollyWoozle
    Awesome article! Thanks!
  4. alexa009
    I have done the egg float test before, at least we know it's a fact and not a theory, all of the bad eggs always smell bad when cracked open while the good ones don't smell at all.
  5. BReeder!
    Very interesting. Being new will to bring chickens, I found these words of wisdom helpful. Thank you for taking the time to share.
  6. I am the Walrus
    Good article. Well written.
  7. rtj18175
    I have two ducks and they LOVE mud puddles. Is there a reason for this?
      Smury739 likes this.
  8. VanguardGirl404
    I love how they will crowd into the same nest box, that's cute.
  9. blackbelt
    Humm interesting. I've had chickens all my life and still do here on the homestead,I never wash my eggs and if I do have to them they are in the refrigerator. If not they go in a basket on my kitchen counter.
      Skipper81 likes this.
  10. FrankiesFamFarm
    better late than never - fantastic and super informative. I feel i learn so much every time i pop onto this site. thank you!!
      Skipper81 likes this.
  11. Featherbrain1986
    "Opened far from your nose."

    Haha this cracked me up!
    -I formally apologize for the ridiculous pun!
    1. 4hmomof4
      Puns are amazing. No apology needed lol
  12. Littlefaceza
    Very informative!! Thanks very much :)
      Skipper81 and black_dove2 like this.
  13. Jnkmoultonr1
    So infomative. Wow several things i didnt know. Alot of helpful information. Thank you very much
      Skipper81, Enrique86 and black_dove2 like this.
  14. SonOfSA
    Thanks for all the information.
    Very interesting.
      Skipper81 and black_dove2 like this.
  15. Miamoo
    Great information. Learned some new things about chickens.
      Skipper81 and Curnow like this.
  16. Farmer Niz
    Do you have recommendations for egg collection keeping them safe to eat?
    - How soon after do they need to be collected?
    - Is it okay to put them directly into the fridge, whether they are warm or cool to touch?
    - Any other info that comes to mind to share...
      Skipper81, DrStein and black_dove2 like this.
    1. Chicken Huck
      You do not have to refrigerate the eggs that you gather from your flock. The only reason you need to refrigerate eggs is if they are over a month old. The eggs you buy at the store must be refrigerated because they are usually at least a week and sometimes as much as three weeks old by the time you purchase them. Consider this, a hen lays no more than one egg a day, some breeds only two to three eggs a week. She lays a clutch, usually 12 to 18 eggs, and she hatches most of them. None of them have been refrigerated. If they were, they probably wouldn't hatch. If they are good enough to hatch after sitting in a nest outside for two to three weeks before she begins brooding, they should be good to eat for at least as long. By the way, if you plan to boil your fresh laid eggs you need to let them sit in a cool (about 72 degrees) place for at least three days before boiling them so you will be able to peel them.
  17. extrememainer
    I think that the picture of the Silkie is adorable
      Skipper81 likes this.
  18. DolittleFarm
    Thanks for the great info
      Skipper81 likes this.
  19. luckychick105
    Excellent article, Thanks
      Skipper81 likes this.
  20. Chicken Wisperer
    Great article, I really have a new appreciation for my chicks and their eggs. They are amazing birds.
      Skipper81, Jnkmoultonr1 and Curnow like this.
    1. extrememainer
      I think we can all agree on that
      Skipper81 and Jnkmoultonr1 like this.
  21. fatchic
    I got my first egg this morning. It's bumpy and very skinny. it wasn't laid in the nesting box. It was on the ground in a corner of the coop. I am wondering what now? Do I need to change the food, give laying feed, stop scratch...
      Skipper81 likes this.
    1. Lisa Wood
      Mine did that. Make the best box visible, and I put golf balls in to encourage them. Once one starts laying in a box, I think the rest will catch on. My eggs looked small and funny at first, but they will become beautiful and get bigger.
    2. extrememainer
      Mine did the same but then after a while they started laying regular normal eggs. But I love the golf ball idea!!!!!!
      PINKCHICKENLADY and fatchic like this.
  22. Stellaminpin5
    Super cool article! I love to read this kind of article!
  23. lindamiller
    Always enjoy reading new articles about chickens, their egg laying habits and different personalities of the flock...Thanks for all the information...Appreciate!
      Skipper81 and Jnkmoultonr1 like this.
  24. Ocala RIR
    Got a question? I get fertile eggs from a farmer and he said layer feed affect the pure egg for fertilization. It's an argument because I think proper nutrient needed for the hen to make good eggs for fertilization. So who is right?
    1. Chicken Huck
      I feed layer feed to my hens during laying season, have been doing this for somewhere around 40 years. Only effect I have seen is more eggs. If I have a broody hen that I can isolate she will commonly hatch all or nearly all the fertile eggs. In incubator I get about 85% hatch from fertile eggs. I think this farmer is pulling your leg.
  25. Mountain Peeps
    Egg-cellent article.
      Skipper81 and SonoranChick like this.
    1. extrememainer
  26. lindamiller
    Interesting and answered some of my questions...Thanks! enjoyed!
      Skipper81 and Ronnie2 like this.
  27. gunnermccaw
    Everything I wanted answers for and such an easy read. Were you reading our minds?
      Skipper81 and jackiedee like this.
  28. lindamiller
    Loved your article...I have ten hens and they usually lay nine to ten eggs a day...Yesterday I only got six eggs...We live in Florida ...the temp and humidity dropped slightly but not enough to make a big difference. Although the days are getting a little shorter...Should I feed them earlier in the AM.? Or is this just normal every now and then?
      Skipper81 likes this.
    1. Chicken Huck
      Normal. As the days get shorter some hens tend to quit laying. You can stop some of this by giving them additional artificial light. You need nothing more than a 100 watt light bulb left on for about 4 hours after dark. A regular household timer works well. As long as the temperature can be kept above 45 degrees.
  29. mumofsix
    Wonderful article! Thanks
      Skipper81 likes this.
  30. eggbeforchicken
    great job //////////// as for the golden egg layer you first get an golden egg then its easy
      Skipper81 likes this.
  31. Donnah23
    great news thanks...
      Skipper81 likes this.
  32. WendyF
    I loved this article! Thank you so much!!
      Skipper81 likes this.
  33. fairfeatherfriend
    Thanks for the great post that keeps on giving good info, now two years later! Can't help with the golden eggs, but maybe a good fairy will wave a magic wand for you. :)
      Skipper81 likes this.
  34. Whitehouse10
    Thanks for the info , very helpful
      Skipper81 likes this.
  35. nate1the1great1
    Wow great job i thought i new a lot about chickens now i know more lol
      Skipper81 likes this.
  36. poodlechicks
    Very good article for beginners. Well written!
      Skipper81 likes this.
  37. PeckPeckChick
    To make your egg yolk orange add dried marigold petals to the feed, great article btw
      Skipper81 likes this.
  38. AnnHolden
    Very nice . Answered any and all questions i would have had without any mumbo jumbo that someone would have to look up to understand . Thank you for keeping it simple and to the point .
      Skipper81 and Shiyanne like this.
  39. danceinchicken
      Skipper81 likes this.
  40. frodazoey
    Thank you for posting your knowledge of eggs.
    Very easy to read and understand.

    I have so much to learn.
      Skipper81 likes this.
  41. Cheepskate
    Very informative and well written article. Thank you!
      Skipper81 likes this.
  42. Sandywitch
    Wow! This article was packed with useful information as well as done in and easy-to-read and interesting manner. I have a memory like a sieve, so I'll refer to it often!
      Skipper81 likes this.
  43. crazyfeathers
    Wonderful article. Could you do another on chicken breeds or illnesses. Thanks learned some new things.
      Skipper81 likes this.
  44. Mrs. Mucket
    Correcting myself: actually the white and yolk do not LOOK the same in any egg! There can be variations in color, texture, and fluidity, and there can be spots in there too. But generally most eggs are very similar with clear/opaque albumen and a yellow yolk.
      Skipper81 likes this.
  45. Mrs. Mucket
    Aliprowl--I meant that the white and yolk inside are the same in any egg. I guess I could have made that more clear!
    Kerry Harrigan--I have never raised ducks and I don't know the answer to either of your questions. This would be a good question to post in the duck secion of the BYC forum! Find it here:
      Skipper81 likes this.
  46. Kerry Harrigan
    How long before a female duck will begin to lay eggs. Is it ok that I have 3 males and 1 female?
      Skipper81 likes this.
  47. brendi
    WOW Great Information!!!! Thank-You :)
      Skipper81 likes this.
  48. Valk
    I just learned so much, what a terrific article!
      Skipper81 likes this.
  49. aliprowl
    Great information - very interesting! One quibble - my Easter Egger eggs are blue or green all the way through the shell. The interior of the egg isn't white, as you say, unless I am misunderstanding your point - " the eggs inside are the same as eggs of other colors..."
      Skipper81 likes this.
    1. Chicken Huck
      The egg shell of certain breeds has bile added to the shell during formation making the eggshell blue. Brown eggs have a white shell with pigments added to the outside, Their are several genes that determine the amount of pigment deposited on the shell. This is why some breeds lay darker eggs than others. Olive eggs are eggs with blue shells and brown pigment on the outside. The brown eggs usually get lighter as the hen lays her clutch.
  50. TheChickenMan13
    Great article!!! literally every question I have about my chickens eggs is right here in this short read!!! Thank you!
      Skipper81 likes this.

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