How Do Roosters Fertilize Eggs: All You Need To Know

Have you ever been confused about how roosters fertilize eggs?

Many people think that roosters fertilize the egg after it has been laid.

This is not correct.

Understanding how chicken courtship, mating, and egg fertilization works is important for backyard chicken keepers.

Many roosters frequently mate with hens regardless of whether you want to breed them. Some chicken keepers may mistake mating for aggressive behavior if they do not know what to expect. Roosters also exhibit odd behaviors during courtship that could alarm first time keepers.

Keep reading to understand these mating behaviors and to learn how roosters fertilize eggs…

Chicken Courtship 101

Rooster With Hens

Before you learn how roosters fertilize eggs, you need to understand chicken courtship.

Chicken courtship is a complex series of behaviors between a rooster and hen. Many first time chicken keepers are confused by courtship behavior. It can be difficult to figure out when courtship is happening if you do not know what to look for.

This is especially true when the hen rejects the rooster and no mating occurs. To the untrained eye a rooster’s attempt to court a hen may look like meaningless backyard antics!

However, courtship behavior is far from meaningless. It is a communicative dance between a rooster and a hen. The rooster always takes the first turn. He starts by doing a sideways shuffle towards the hen he is interested in. During this shuffle he approaches the hen from the side.

He will then lower one wing and circle the hen. Depending on the hen’s behavior he may or may not make a full circle around her.

This is an odd sight to see because the rooster spreads one wing out towards the ground. When seeing it for the first time you may think that there is something wrong with his wing. However, there is nothing wrong with him and this is normal chicken behavior.

If a rooster does the wing dance near a hen, he is trying to court her. However, if a rooster drops a wing and circles around you or another rooster, it is more likely that he is trying to assert dominance.

Once the rooster has performed the wing dance for a hen it is up to the hen to either accept or reject his advances. If she is interested she will communicate to the rooster by crouching down while dipping her head and body towards the ground.

This allows the rooster to easily mount her for mating.

If the hen is not interested in mating then she will reject his advances by walking away and avoiding him. Some roosters may be especially pushy and continue trying to court with the hen until she changes her mind. This is seen most commonly in younger roosters.

Eggs are not fertilized during courtship. That occurs after mating, which is explained in the next section.

How Do Roosters Fertilize Eggs

Rooster and Hen Mating

Once the courtship is complete the rooster will mount the hen.

The rooster will grip the back of the hen’s head with his beak. Some roosters may grab the feathers at the back of her neck while others may even grab her comb. Regardless of what he grabs for support, he needs to hold on tight to not fall off.

Once the rooster feels secure on top of the hen, he will tread on her back for a few seconds by scratching at her with his feet.

Sometimes your hen might get injured from too much treading. If you see this happening with one of your hens, then you can use a chicken saddle. This is a piece of thick fabric that is secured to a hen’s back to protect her.

After treading the rooster performs the cloacal kiss.

The rooster must dip his tail down to the side of the hen’s tail and spread his tail feathers. He will then press his cloaca to the hen’s cloaca and release sperm into her. Once this has happened, mating is complete.

Mating is a very quick process that lasts only a few seconds.

At this point you are probably wondering, how is the egg fertilized?

A rooster fertilizes an egg by mating with a hen and placing his sperm into her cloaca.

However, this is the simplified story of fertilization. Once the rooster’s sperm is inside the hen, it goes on quite the adventure before it fertilizes any eggs.

Hens have sperm storage glands inside of their bodies and they can store sperm for somewhere around 2 weeks.

When a chicken is about to lay an egg, the egg will press on the sperm storage glands and release some sperm back into her reproductive tract.

The sperm will not fertilize that particular egg as it is surrounded by an eggshell that prevents fertilization.

Instead, the sperm must travel all the way up to her oviducts. Here, the rooster’s sperm will come into contact with the hen’s next egg. Eggs in the oviduct have just been ovulated and do not yet have a shell that can block the sperm. The sperm will fertilize this egg.

Chicken Egg Fertilization Timeline

Egg Candling Chart

Step 1: Courtship

Courtship is when a rooster communicates to a hen that he is interested in her by performing a special dance. If the hen is impressed she will crouch low to the ground and allow the rooster to mount her for mating. Courtship may last a couple of seconds or several minutes depending on the hen.

  • Timescale: Minutes before mating

Step 2: Mating

Mating only lasts a couple of seconds. During mating the rooster mounts the hen and they perform a cloacal kiss where the rooster passes his sperm into the hen’s reproductive tract.

Step 3: Sperm Storage

The rooster’s sperm travels a short distance into the hen’s reproductive tract until it reaches the sperm storage glands. Sperm will enter the storage glands and can live in there for between 1 and 4 weeks.

  • Timescale: Minutes after mating

Step 4: Sperm Release

The sperm is released from the storage glands and will travel deeper into the hen’s reproductive tract. Its final destination is the left oviduct. If your hen is a prolific egg layer she might release sperm minutes after mating. However, if she only lays one egg a week it could be a whole week until she releases the sperm.

  • Timescale: Minutes to days after mating

Step 5: Egg Fertilization

Once the sperm is in the oviduct, it waits for the next egg to be ovulated. Once the egg is ovulated, the sperm will fertilize it by joining together with the egg.

  • Timescale: One hour to four weeks after last egg was laid

Step 6: Egg Laying

The egg is fertilized very early on in the laying process. It will take 26 hours for the fertilized egg to fully develop and enter the world as an egg.

  • Timescale: 26 hours after fertilization

Overall, after mating it can take anywhere from 27 hours to 7 days for the first fertilized egg to be laid.

Read How Do Chickens Make Eggs for more.

Identifying Fertilized and Unfertilized Eggs

Egg Candling

There are two easy ways to tell if an egg is fertilized or unfertilized.

The quickest way is to crack the egg open and look at the yolk. Each egg has a tiny white spot in the yolk. This white spot is called the germinal spot. In eggs that are not fertilized, the germinal spot is a small collection of the hen’s egg cells. However, if the egg is fertilized by the rooster, the germinal spot will be bigger and appear as a circle with a white outline.

The germinal spot method works great if you are about to eat the egg. However, many people want to know if eggs are fertile because they want to hatch a chick.

You will need to candle these eggs.

Candling allows you to see inside the egg without breaking the shell.

All you need is a flashlight, a dark room, and the egg. Candling should be done after the egg has been incubated for 7-10 days. In the dark room, turn on the flashlight and hold it up to the larger end of the egg.

If the egg looks like it has a dark web inside of it, then your egg is fertilized.

Whereas if you see no dark structures within your egg it means that your egg is not fertilized.

How To Tell Which Rooster Has Fertilized An Egg?

Maybe you want to know if a particular rooster fertilized a particular egg.

How can you tell?

First, make sure that the egg in question is fertile using the above methods.

If you have only one rooster in your flock, this is easy.

If you have two or more roosters who both mate with the same hen, it is possible that either of them could have been the one to fertilize her eggs. The only way to tell who the father is would be to figure out whose genetics the chick inherited after hatching.

This can be very difficult, especially if the roosters in question are similar.

Frequently Asked Questions

Do roosters fertilize eggs after they have been laid?

No.

Roosters fertilize eggs about 26 hours before they are laid.

The eggs are actually fertilized inside the hen’s oviduct, before the egg white or egg shell is added to the egg.

Does a rooster fertilize every egg?

Not always.

If a hen is frequently mating with only one rooster, he will fertilize most of her eggs. However, it is still possible that the occasional non-fertile egg will slip through.

How long does a rooster have to be with a hen before the eggs are fertile?

On average, it takes new roosters 4–7 days to make their way around and mate with most of the hens.

Fertilized eggs can be laid in a minimum of 27 hours after mating if the hen is in the right stage of her egg cycle and lays eggs frequently.

Summary

Now you know exactly how roosters fertilize eggs.

If you are trying to breed your own chickens you can also troubleshoot why breeding is not working.

Is the rooster uninterested and not even courting the hen? Or is the hen rejecting his advances? You can tell if it is a fertility problem if you see the rooster mating with the hen but only candle unfertilized eggs in the following weeks.

Even if you are not breeding, you can now watch the social dynamics between hens and roosters in your flock and know more about what is going on in their lives.

Let us know in the comments section below if you have any questions about roosters mating and fertilizing eggs…

Chris Lesley Bio Picture
Chris Lesley has been Raising Chickens for over 20 years and is a fourth generation chicken keeper. She can remember being a young child when her grandad first taught her how to hold and care for chickens. She also holds a certificate in Animal Behavior and Welfare and is interested in backyard chicken health and care.

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