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The 4-1-1 of Chicken Reproduction

Did you know chicken reproduction isn’t the same as other barnyard animals or even other birds?

Yep, your fine feathered beauties have a unique procreation system. 

Let’s take a look at the 4-1-1 of chicken reproduction from the mating to the chick.

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A rooster in a flower field.

Anatomy of Mating

The surprising anatomy of a hen is that she has two ovaries, but only the left one is functional. 

Hens and roosters do not have outside genitalia but instead use an external orifice called the cloaca. When the cloaca touch together, sperm is transferred into the hen referred to as a “cloacal kiss.” 

The cloaca or vent is also where waste excretes. To protect the egg from touching any feces, the hen’s uterus turns inside out beyond the cloaca (vent) when laying occurs. That way, the egg is not contaminated by excretions.

When chickens mate, the rooster jumps on top of the hen, using his talons to grip her back, and often biting her back neck feathers as well. The rooster will touch his cloaca to hers in a few swift movements, then jump back off.

Roosters tend to choose favorite hens that they mate with more often. These hens may lose feathers on their back from the constant action. Many chicken keepers use chicken saddles to protect these hens, or separate them from the rooster until their feathers have recovered.

Chickens mating.


Fun Fact: A rooster’s sperm is viable for two weeks to 30 days! 

Amazing, right?

The ovum (yolk) starts as one cell and enters the oviduct, which is a 25-27 inch winding tube. The first section in that tube is the infundibulum, and once the ovum enters it, this is where fertilization takes place. The yolk stays in this section for 15-17 minutes.

The Formation of the Egg

The magnum section of the oviduct is thirteen inches long, and the yolk takes three hours to travel through as the thick albumen or egg white forms around it.

Then on to the third section, called the isthmus, which is just four inches long. Just as its name implies, it is a restricting section that forms the inner and outer shell membranes. This process takes seventy-five minutes.

Next up is the shell gland, which is another four to five inches in length. The shell forms around the egg in this section, taking up to twenty hours to complete the transformation. This is where the eggshell also receives its color through a pigment.

The egg then moves on to the uterus. Here it enters small end first then turns to the large end coming out first. The muscle of this area helps to push the egg out by extending itself with the egg and turning inside out to expel it. 

Do Hens need a Rooster to lay eggs?

As we have seen, a hen stores sperm in her body and can lay fertile eggs for many weeks without any contact with a rooster. 

Mating is not a requirement for egg-laying.

Light is the stimulus for a hen’s egg-laying process, not romance. Hens are programmed to lay eggs when light is plentiful, spring and summer. 

However, if you desire a fertile egg to hatch the rooster is a must.

A red rooster.

How can you tell if an egg is fertilized?

There are a couple of ways to tell…

Take a warm bowl of water and carefully place an egg into it. If an egg gently glides to the bottom, it’s good news. The weight of an embryo will help keep it at the bottom. 

Candling is the best way to “see” into the egg. If you detect a group of blood vessels, what looks like an eye or even an outline or shadow of the chick’s body, then you have a fertilized and developing egg.

Cracking an egg open is also a way to check for fertilization. If the egg is fertilized but hasn’t been incubated, you will find a white bullseye on your egg yolk, which is two rings of white, one inside the other.

Three chicks standing next to a broken egg.

Brooding or Incubation?

Now that you know your eggs are fertile you may be wondering whether you should allow your broody hen to take over or try incubation.

There are several factors to consider, and you can read more about that: Hatching Eggs: Broody Hen or Incubator Which is Best? 

But for this article, we will look at just a couple of factors: time and money. A broody hen can save you both by taking on the job herself. There is no need for the expense of an incubator or continual turning and checking. 

However, the awe and wonder of hatching chicks and becoming a chickie mommy have its appeal.

A chick hatching out of an egg.

These are just a few of the basics of chicken reproduction. If you would like to learn more check out Penn State’s article: Avian Reproductive System

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