How Are Chicken Eggs Fertilized?

chicken egg

Written by Jennifer Gaeng

Updated: September 20, 2023

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Did you that hens can lay eggs without a rooster? Fertilization of the egg is necessary for the hatching of a chicken. The vast majority of store-bought eggs come from hens that have never been exposed to male sperm. In most cases, laying hens at commercial farms have never come in contact with a rooster. Without the help of the male sex, our hens would still lay an egg every day. On the other hand, if you want fertile eggs from your chickens, you’ll need a rooster to do his job, which he’ll do happily and regularly.

A rooster is determined to fulfill his biological duty of reproducing and spreading his genes throughout the earth. So, the topic of today’s post is the process of fertilization, including its causes and your role in producing fertilized eggs. We will cover the six stages of fertilization, the five stages of chick development, and how to tell the difference between a fertilized and an unfertilized egg!

How Do Chickens Have Their Eggs Fertilized?


It is the rooster’s job to fertilize the hens’ eggs.

© Decout

It is the rooster’s job to fertilize the egg by inserting its sperm into the hen’s cloaca during mating. In reality, the process of fertilization is more complex than this brief summary suggests. The journey of the rooster’s sperm within the hen is rather arduous until it finally reaches the eggs and fertilizes them.

Hens can store sperm for up to two weeks in their internal sperm storage glands. The egg presses upon these sperm storage glands just before a chicken lays an egg, releasing some sperm back into the reproductive system.

Because of the protective shell around the egg, the sperm will be unable to fertilize it. The sperm has to make it all the way to her oviducts instead. This is where the rooster’s sperm will meet the hen’s nest egg. Ovulated eggs inside the oviduct have not yet developed a protective shell to keep out sperm. With the help of the sperm, this egg will develop into a baby chick.

The 6 Stages of Chicken Egg Fertilization

Phoenix chicken

A rooster must mate with a hen in order to fertilize her eggs.


The First Stage: Courtship and the Countdown to Mating

During courtship, a rooster dances specifically for the purpose of showing an interested hen his affection. When the hen is ready to mate, she will squat down low and let the rooster mount her if he has impressed her. Depending on the hen, courtship might last anywhere from a few seconds to many minutes.

The Second Stage: Mating

It takes only a few seconds to complete a mating. While a rooster is mating with a hen, he will mount her and give her a cloacal kiss, which will allow his sperm to enter the hen’s reproductive system.

The Third Stage: Sperm Storage

The rooster’s sperm only has to travel a short distance through the hen’s reproductive system to reach the sperm storage glands. This happens within minutes of mating. The average lifespan of sperm in the storage glands is somewhere between one and four weeks.

The Fourth Stage: Sperm Release

Released from the sperm storage glands, the sperm will move further into the hen’s reproductive system. The left oviduct is its ultimate destination. Even within minutes of mating, your prolific egg layer hen may start releasing sperm. But, when she only produces one egg per week, the sperm may have to wait a whole week before being released.

The Fifth Stage: Fertilization of the Egg

After entering the oviduct, the sperm awaits the next egg to be released. As soon as the egg is released during ovulation, it will connect with sperm to become fertilized. This happens one hour to four weeks after the last egg was laid.

The Sixth Stage: Egg Laying Time

Fertilization of the egg occurs quickly after it has been laid. The time between fertilization and the egg’s birth into the world is 26 hours. The very first fertilized egg may be deposited anywhere from 27 hours up to seven days post-mating.

The 5 Stages of Chick Development

baby chicken siblings

Baby chicks typically hatch within 21 days of fertilization.


First, the egg undergoes fertilization during mating; then, around 24 hours later, it is deposited.

Second, the embryo is able to begin its growth thanks to the hen’s body heat. A cell divides into two within a few hours of fertilization, and subsequently into four, eight, sixteen, and so on.

The third step is that once the egg is laid, the temp drops and cell proliferation ceases. Warmer temperatures, though, can reignite the process.

The fourth step is to either have a mother hen incubate the eggs or place them in an incubator.

Fifth, if the conditions are right, the chicks will begin to develop and expand, and they will begin to hatch in 21 days (can be longer if a hen is the one doing the incubating).

Incredible things happen from the first day of incubation until the day the eggs hatch. Eggs need to be kept at the ideal temperature, flipped every couple of hours for the majority of the day, and subjected to carefully managed humidity levels. There is a lot involved, but the hen knows what she is doing!

Fertilized vs. Unfertilized Chicken Eggs

chicken eggs in a nest outdoors

When a chicken egg is fertilized the white dot in the yolk of the egg expands and takes the shape of a white circle.


A fertilized egg can be identified by one of two distinct characteristics. Looking at the yolk of an egg is the quickest method. There’s a little white dot in the yolk of every egg. The germinal spot is the name given to this tiny white dot. The germinal spot is a cluster of unfertilized hen’s egg cells found in unhatched eggs. When a rooster fertilizes an egg, the germinal spot expands and takes the shape of a white circle.

For situations in which the egg will soon be consumed, the germinal spot approach is ideal. Many would like to hatch a chick, but first, they need to know if the eggs they have are fertile. These eggs will need to be candled. To examine what’s within an egg without cracking the shell, try candling. There’s nothing more required except a dark room, a flashlight, and the egg.

When candling, wait until the egg has been in the incubator for at least 10 days. Lighting the chamber with the flashlight, you’ll hold it up to the egg’s larger end in the dark. When an egg develops a dark web inside, it means it has been fertilized. A fertilized egg will have black structures within it, but an unfertilized egg would not.

Questions & Answers

To What Extent Do Roosters Play A Role In The Fertilization Of Eggs?

Fertilization by roosters occurs roughly 26 hours before an egg is laid. Eggs are fertilized before they are even covered with a shell in a hen.

Could Every Egg Be Fertilized By A Rooster?

Certainly not in every case. Every hen’s eggs will be fertilized by the same rooster if she mates with him repeatedly. Although this is unlikely, it is possible that a single infertile egg could make it through.

How Long Does It Take For A Rooster To Fertilize A Hen’s Eggs?

A new rooster needs between four and seven days to mate with the majority of the hens. If the hen is in the appropriate stage of her egg cycle and lays eggs regularly, fertilized eggs can be laid in as little as 27 hours after mating.

Barnevelder rooster isolated

Roosters will breed with any type of hen.


Bonus: Do hens and roosters have to be the same breed to produce chicks?

No, a rooster will mate with any type of hen and vice versa. There are no problems associated with hatching mixed-breed chickens – as a matter of fact – it is fun to see how they turn out! Cross-breeds can result in beautiful plumage, new egg colors, prolific egg-laying, hardiness, and friendly personalities.

Mixed breeds cannot be used for show – even if they are the most gorgeous chickens you’ve ever seen. Some chicks may turn out a little bit quirky – but that’s fun too!

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About the Author

Jennifer Gaeng is a writer at A-Z-Animals focused on animals, lakes, and fishing. With over 15 years of collective experience in writing and researching, Jennifer has honed her skills in various niches, including nature, animals, family care, and self-care. Hailing from Missouri, Jennifer finds inspiration in spending quality time with her loved ones. Her creative spirit extends beyond her writing endeavors, as she finds joy in the art of drawing and immersing herself in the beauty of nature.

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