Facts about eggs

Eggs comes in many sizes and colors

Curious about the fascinating world of hens and eggs? We’ve gathered 55 interesting facts about eggs to address some common questions and delve into various aspects of egg production, egg variations, and the role of roosters in the process.


Hens and Eggs

  • Female chickens, known as pullets in their first year, typically start laying eggs at around 20 weeks of age.
  • Different chicken breeds have varied laying patterns, with some producing eggs daily, others every other day, and some only once or twice a week.
  • Certain individual hens may never lay eggs due to factors like narrow pelvises or anomalies.
  • Hens’ laying routines can be disrupted by factors such as molting, lack of daylight in winter, temperature extremes, illness, poor nutrition, stress, or insufficient access to fresh water. They usually return to normal laying habits when the disruptive factors are resolved.
  • Most hens maintain productive laying for about two years before a decline, but some continue to lay eggs for several years.
  • Hens lay eggs regardless of whether they’ve encountered a rooster; roosters are only necessary for fertilizing eggs.

You can find additional information about chickens and eggs here.

Interesting facts about eggs


Egg Development and Laying Process

  • Female chicks are born with undeveloped yolks called ova. Once they mature, an ovum is released into the oviduct for development.
  • A productive hen typically has eggs in various stages of development within her reproductive system.
  • It takes approximately 25 hours for an egg to travel from the ovary to the vent for laying. During this time, the yolk grows, surrounded by egg white, enclosed in a membrane, and encased in a shell, with pigment deposited as the final step.
  • Fertilization occurs if sperm is present before the albumen is deposited.
  • Yolk provides nourishment to a developing chick embryo, while albumen cushions it.
  • Although hens have a single exterior opening for laying and elimination, two separate channels—the oviduct and the large intestine—open into this cloaca. The egg passes through the cloaca without contacting waste matter.
  • The typical interval between egg laying is approximately 25 hours.
  • Hens usually avoid laying eggs in the dark, so once their laying cycle reaches dusk, they typically wait until the following morning.
  • Eggshell production depletes calcium from a hen’s body, resulting in fading of comb, wattles, legs, and ear lobes. Calcium must be replenished through feed, supplements, or calcium-rich soil for outdoor-access birds.


Facts About Egg Variations

  • Young pullets may initially lay malformed eggs, while older hens may occasionally lay abnormal eggs due to age, stress, or illness.
  • The first eggs from a pullet are smaller than those produced as she matures.
  • Terms like “fart egg” and “oops egg” refer to tiny eggs that pass through the oviduct without reaching full size.
  • Shell-less eggs lack a shell, potentially having membranes or just yolk and white.
  • “Double eggs” or “egg in an egg” result when an egg with a shell is enclosed by the next egg in the oviduct, which also forms a shell.
  • “Double yolkers” may have normal egg white with two or more yolks and larger shells.
  • “Yolkless eggs” consist of egg white alone.
  • Occasionally, eggs may have wrinkled, misshapen, rough, bumpy, or unusual-colored shells.
  • Egg size varies based on breed, age, and the hen’s weight, with larger breeds typically producing larger eggs.
  • Shell color depends on the breed, with most laying light-to-medium brown eggs, while a few breeds produce white, dark brown, green, blue, or cream-colored eggs. Shell color doesn’t affect the egg’s interior.
  • Shell color intensity in eggs from one hen may vary over time.
  • Some eggs may have a chalkier texture, depending on the breed or individual hen.

Egg size varies based on breed, age, and the weight of the hen


Nesting and Behavior

  • Hens often share nest boxes, so it’s unnecessary to provide one for each hen.
  • Some hens prefer privacy while laying eggs, while others nest together, sometimes crowding into one box.
  • Occasionally, hens will lay eggs in separate locations or join others in a nest box.
  • Hens may sing the “egg song” before or after laying an egg, a cheerful announcement.
  • Chickens learn by example, so leaving fake or real eggs in designated nest boxes can encourage them to lay there.
  • Unconfined hens may lay eggs outdoors if they don’t return to the nest box, sometimes resulting in surprise chick appearances.
  • Chickens may eat their own eggs, even accidentally broken ones.
  • Some chickens become habitual egg-eaters, and such birds should be removed from the flock to prevent others from learning the behavior.
  • Holes in eggs or cracked eggs may not necessarily indicate egg-eating, as hens can accidentally crack eggs during nesting or out of curiosity.
  • Chickens can be fed their own or other eggs, either raw or cooked, as they provide valuable nutrition.


Roosters and Their Roles

  • Roosters are primarily required for fertilizing eggs, but they also serve as watchmen, alerting hens to predators and searching for food.
  • Not all eggs will be fertile, as some hens may not interest a rooster, and roosters may favor certain hens.
  • Hens do not have an estrus cycle and can mate and produce fertile eggs at any time.
  • Sperm can remain viable in a hen’s oviduct for three to four weeks, fertilizing multiple eggs.


Brooding and Hatching

  • Any breed of broody hen can be used to hatch eggs and raise chicks from other hens.
  • Broody hens may sit on any eggs, fertile or not, and sometimes gather eggs laid by other hens.
  • During brooding, extra eggs can be removed daily from the clutch, with pencil lines drawn around the eggs intended for brooding.
  • A setting hen typically leaves the nest daily to eat, drink, and defecate without affecting egg viability.
  • Chicken eggs usually hatch about 21 days from incubation or nesting, with some variation among breeds.
  • Not all fertile eggs develop embryos, and not all chick embryos successfully hatch.
  • Broody hens may push out eggs they sense are not viable.


Facts About Egg Characteristics

  • A typical fresh egg comprises a yellow yolk, thick and thin layers of albumen (egg white), and chalazae, which anchor the yolk to the white.
  • A large chalaza doesn’t indicate embryo development in an egg.
  • Fertile eggs have a visible blastoderm with a ring, while infertile eggs have a solid white disc.
  • Fertile eggs are edible, and while some consider them more nutritious, scientific research hasn’t confirmed this.
  • The color of the egg yolk depends on a hen’s diet, with foraging hens or those fed kitchen scraps producing varied yolk colors.
  • Blood spots and meat spots in eggs are harmless bits of tissue and are allowed in commercial Grade B eggs.
  • Eggs have a protective coating that prevents bacterial entry; washing should be done just before use