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


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  1. Lothiriel
    Wonderful article! I loved reading it. Great job!!
  2. CarolJ
    You did a great job - and you sure got a lot of information into one article. I thought I already knew a lot about eggs - but I learned a couple of new facts. Thanks - and congratulations!
  3. DNCXmom
    This was a great article. Thank you so much. I found a lot of useful information in it.
  4. bwalden
    Very good article.
  5. CityGirl35
    Excellent reading! I too learned a few new facts. What a wonderful community this is, and I am grateful for all the expertise shared. Thank you!
  6. orumpoultry
    Loved the article, even learned a few new facts! Thanks!
  7. applegal
    Wow... everything you wanted to know about eggs summed up. Thorough, but quick and easy to read. Thank you.
  8. simone jone
  9. chickens4fun215
    Great article
  10. PeeperKeeper
  11. Sailing Dede
    Nice one, and what a cute silkie pic. I so want one!!!! :)
  12. CountryRoosterUSA
    Congratulations, wonderful information, good job.
  13. shelleyrobertso
    from your information you say the sperm of a rooster can be present for weeks. I have to two roosters Brahma and Ameracauna. I have both types of hens. I seperated the breeds just recently so the same breed rooster could mate with the same breed hen. I started to collect eggs to put in the incubator. After reading this information am I right that I have to keep them seperated 4-6 weeks before I start to collect eggs to ensure a pure Ameracauna???
  14. nicola86
    Love it. Great information - learnt lots of new stuff
  15. ninabeast
    Oh, BRAVA!!!!
  16. Novaleigh
    WOW! Learn something new every day! Fantastic list of great facts!
  17. iluvsedward
    Good for newbies!
  18. californiagirl
    thanks so much!
  19. 6lilhens
    Thanks so much! You gave a lot of great info on eggs! Loved it.
  20. thatbethchick
    Very Good, thank you!
  21. somadlyinlove
    Very good job!
  22. ChickendeVille
    Great article! People ask me all the time about eggs and this sums it all! I am sharing this...
  23. MusicGarden
    Very appreciative of this collection; extremely informative and super organized! Thank you!
  24. rapturecidal
    Excellent, alot of information about eggs. And i needed it too.
  25. rapturecidal
    Excellent. Alot of facts about eggs and i needed them too. Thanks.
  26. 202roosterlane
    Loved reading all of this. Great info. Thank you.
  27. KristyAz
    Nice job on this!
  28. lifefromthelog
    I love this artilce!!! I learned sooooo much about my chickens eggs! Thank you!
  29. jstagrl8110
    Awesome!!!! Just read most of it outloud to my husband.
  30. pax12
    Great Job!!!!!!
  31. chanelle
    Very well written !
  32. kabaluch76
    Really enjoyed this information! :) Thanks for doing it.
  33. vtnoel
    Thanks for a great article! We are just starting out and your information was super helpful!
  34. berniezahm
    Interesting information. However the blue eggs laid by Araucanas have the color in the shell material. Unlike other chicken eggs that are white on the inside they are blue on the inside also.
  35. DeWalt
    Great arcticle. Thank You, very informative
  36. baby01
    that is good job, thank you so much
  37. JerseyBean
    Thank you so much for the great article, i really enjoyed reading it and learnt so much.
  38. Mrs. Mucket
    Thanks all for your comments!
    Berniezahm--Thank you for adding your info on Araucana eggs. I like to keep learning too!
    Shelleyrobertso--The partial answer to your question is yes, it necessary to separate your flock if breed-specific fertilization is your goal. My understanding is that the length of time varies but I don't know if that is breed-specific or depends on the rooster and/or hen. Maybe someone with more experience or knowledge will chime in here with more details--or you could post a question on the forum?
  39. jandrusrn
  40. Mohawk Chickens
    Thanks for answering lots of un-asked questions that this newbie had.
  41. farmerkay
    I have an egg breaker. How am I going to figure out which of my ten hens is breaking the eggs?
  42. valeriekasnick
    So much good info!! Thank you! Now you've made me want a rooster!! Ha ha ~ I live in the city so "no can do". : (
  43. Mrs. Mucket
    Farmerkay--that is a tough one and I'm not sure of the answer. Hopefully someone reading this can help. Are eggs being broken regularly? I know sometimes I will find a broken egg when the girls all lay their eggs in one pile (one one side of one of two large nest boxes, of course!). Is there any way to separate your hens into groups or isolate any suspects? I suppose if you check frequently you might see a hen in action or find yolk evidence on someone's beak.
  44. girls and guineas
    Enjoyed your article, and learned alot!!
  45. dolrose33
    What a great article. Much info. I am new to chickens or chickens are new to me. I am looking forward to receiving my silkies tomorrow, hopefully. Dolores216
  46. CochinBrahmaLover
    Thanks, so much info!
    I CAN ANSWER YOUR QUESTION- you see, I have a goose who told me how geese lay golden eggs... *whispers in ear* Once you get the egg, grab some golden nylon nail polish, and paint the egg before the dumby hooman comes and grabs it, if the dumby hooman does come, hiss and bite and drive it off!
  47. Fabidon
    Excellent and quite fascinating! Thank you for sharing your wealth of egg knowledge.
  48. 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.
  49. 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?
  50. 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!!

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