The Amazing Egg 🥚
Updated 8th March 2025, First published Thursday May 11, 2017
Which came first, the Chicken or the Egg?
The almighty egg has to be one of the most versatile and fascinating objects ever to have landed on earth. Arriving before the chicken and sometime after the dinosaur it has survived wars, earthquakes and floods of biblical proportions, but how? The answer is simple, the egg is in fact, a master of disguise. It learnt early-on to hide itself inside chickens coming out once a day to have a look around. So there you have it, Omlet has cleared up a question that has been bothering people for centuries, it was obvious really!
How is an egg made?
Chickens are amazing! When your hens are laying well, they will produce a new egg every 25.5 hours. This is a very short time to create something as complex, as perfect and as tasty as an egg.
An egg is made from the inside out. The yolk is made first, and then wrapped in a layer of egg white, before being neatly and beautifully packaged up in an egg shell. The beginning of an egg is the tiny ova which takes a week to grow into a proper egg yolk. If you cut a boiled egg in half and look at the yolk, the dark rings were layers made during the day and the light layers during the hours of darkness. Strange but true! When the yolk is ready it is released along the oviduct. The first part of the oviduct is where the egg white (albumen) is added. The egg white mainly consists of protein, water and minerals. Then the egg carries on along the oviduct where it grows two connecting strands at the top and the bottom called chalaza, which anchor the yolk to the shell keeping it in the centre of the egg.
The next stage is for the shell membranes to form around the white. After this the egg continues down into the uterus where the shell is added. The shell is made from calcium carbonate, which is also found in marble and chalk. The shell is a great bit of design, it is on average only 0.3mm thick but it is incredibly strong.
How does a hen lay her egg?
As a rule, chickens lay in the morning, but each day a little later. Sometimes the last egg of a series is produced in the early afternoon. When it gets too late, they take the next day off. That is why on some days we do not get an egg from each hen. The hen approaches her chosen nesting spot in a very determined yet hesitant way, and finally enters. There she gets comfortable and sits quietly for a long time, often for half an hour or more. She closes an eye, can chat quietly to herself, and possibly re-arranges the shavings, and then finally she gets more exited. Now and then, the hen raises her tail and spreads the feathers of her bottom.
These movements increase gradually. Under her tail, between the feathers, is a small opening with a ribbed rim called the vent. Suddenly the hen stands up with her feet wide apart, tail raised, bottom feathers spread out, and back feathers upright. As her vent opens a little, you begin to see a red membrane. As the hen lowers her bottom, her vent widens rapidly, and the rim is stretched further. The membrane forms a pinkish dome around the egg which is not yet visible at this stage.
1. Ovary, 2. Infundibulum, 3. Oviduct, 4. Magnum & isthmus, 5. Uterus, 6. Cloaca
From rising to dropping
The vent is now wide open, and the ribbed rim has become narrow and far stretched. Through the opening bulges a pink hemisphere of tissue revealing distinct blood vessels. Its top is pointed downward where a new opening arises. The egg appears as a much lighter-coloured disk. The hen strains at intervals. Each time, the egg protrudes a little further out. As it does, the membrane opens to form a red collar around the wider, middle portion of the egg. The membrane will protrude a little way from the ribbed rim. The moist egg pops out.
Sometimes it will come out blunt end first, sometimes pointed end first. For a few seconds after the egg is laid, a small red cone still remains outside, but it is retracted almost immediately and the vent is closed again. The bird stands high above the egg and rests, beak open and panting after her heavy work. The entire process (from rising to dropping the egg) is quite fast and is finished within half a minute. Therefore, it is hard to observe. After a while, the hen looks back, inspects the egg with her beak and leaves the nest under a loud series of cackles.
Why does a hen cackle after laying her egg?
The ancestors of our domestic fowl are the jungle fowl and they were and still are forest dwellers. They live in small family groups called flocks. They scratch under the canopies in the leaf litter and forage for invertebrates, bugs, worms and berries to eat. When a hen goes to lay her egg in the nest the group may wander away through the undergrowth searching for food. The hen's cackle serves to renew the contact with the group as if to shout "where are you?” The rooster (with the other hens) would answer "here we are!” Our chickens like their ancestors still cackle today….sometimes we suppose proudly adding to their call “Wow you should see the whopper I laid today!”
Why do hens leave the nest after laying?
All chickens lay eggs in a series - never more than one per day. If the eggs are not collected, and a good number of eggs are allowed to collect in the nest, the hen may eventually stop laying and start brooding. When the hen leaves the nest after laying an egg, it cools which suspends the development of the embryo inside. This egg and the rest will not develop until the hen takes up residence 24/7 on her nest and starts her brooding. Her body heat coupled with moisture from her skin and the instinct to turn her eggs will hopefully prove fruitful and result in newly hatched chicks 21 days later. So, the idea is all eggs commence development together and hatch together (usually within 48 hours of each other). This is why it is important for the hen to leave the nest after laying because if she went broody when she first started laying then theoretically all her chicks would hatch a day apart and she would leave the nest with the first few hatchlings and abandon the rest. Isn’t nature wonderful!
Do you need a cockerel?
No 😊
Chickens lay quite happily without the amorous intentions of a handsome red wattled male, such as old Perky here.
Should you have a cockerel, you can be sure he will do his best to fertilise the eggs. If a chicken is broody she will then sit on these eggs for 21 days (the incubation period) and with a bit of luck these eggs will hatch and produce more chickens.
The eggs a chicken lays without the help of a cockerel are not fertilised and will therefore never hatch.
Colour of the shell
The colour of the shell depends on the breed of chicken and on the individual chicken itself. Some chickens lay dark brown eggs like the Barnevelder and the Araucana lays a blue egg, but the colour of the shell doesn't affect the taste.
Drop in Egg Production
Pullets need to be close to point o f lay before they even think about laying an egg! Point of lay for commercial hybrids like brown shavers or hyline browns is around 22 weeks of age (later in winter and earlier in summer).
How long this takes depends on the time of year and the individual chicken. Heritage breeds take longer to mature and longer to come into the lay.
Once they are laying though, they may not always produce eggs like clockwork, the reasons could be:
- When your chickens moult their egg production will drop and most likely stop.
- If your birds have had a fright this can result in no eggs for a while.
- Moving birds to a new home or new house can cause a drop in production.
- Egg production is the first thing affected by dehydration. Make sure your birds have plentiful clean water.
- Mites in the hen house sucking the blood of your birds and making them anemic.
- If you are letting your chickens roam about in the garden they may have made a nest under a bush or in a corner somewhere. Follow your chicken discreetly to find the nest, sneaky but necessary!
The Chicken or the Egg?
The age old riddle of which came first, the chicken or the egg' is believed to have been cracked by a team of scientists in 2010. The eggsperts believe the answer is the chicken. The researchers found that for an egg to be made it must have developed in the ovaries of a chicken which means there had to be a chicken before an egg. So that's that one solved!
Now here's the technical bit: A specific protein in the ovaries of chickens, called ovocleidin-17, is responsible for converting calcium carbonate into calcite crystals. These calcite crystals make up the shell of the egg and allow the egg to be laid.
