Fertilized Chicken Egg 101

If you want to expand your backyard flock, you've likely wondered how do roosters fertilize eggs? Learn everything about the chicken mating process and whether your hens actually need a rooster to lay eggs here!

How do Roosters Fertilize Eggs?

If you want to hear the pitter-patter of tiny chicken feet in your backyard or want to try your hand at hatching chicks in an incubator, you'll need a rooster. A rooster will fertilize your hen's eggs, making it possible for them to hatch into baby chicks. 

Chicken mating is an interesting process... to say the least. If you don't know what you're looking at, you'd probably think your rooster is attacking the hen. Chicken courtship is rough and involves a lot of chasing, pecking, and flapping. But don't worry; it's all part of the natural process. 

But how does a rooster fertilize an egg?

I'm going to break down the birds and the bees of chicken fertilization so you can better understand how do chicken eggs get fertilized.

Roosters and Hens: A Match Made in Nature

First things first, let's talk about the birds themselves. Hens are female chickens, while roosters are their male counterparts. Both hens and roosters have reproductive organs necessary for fertilization, which look like this:

Rooster Anatomy

• The Vent: This is the external opening of a rooster's reproductive and waste system, located at the base of its tail feathers.
• Cloaca: This is where both waste and reproductive material leave the bird's body and is located just inside the vent.
• Papillae: Roosters don't have a penis but instead have two small nipples located in the cloaca. The papillae is where sperm is transferred from the rooster to the hen during mating.
• Testes: Where sperm is produced in the rooster's body.

Hen Anatomy

• The Vent: Just like the rooster, the hen's vent is the external opening of its reproductive and waste system.
• Ovaries: Hens are born with two ovaries, but only one is functional. This is where the eggs are produced.
• Oviduct: Once an egg is released from the ovary, it travels down the oviduct and is fertilized by sperm in the hen's body. There are five different sections of the oviduct:
  • Infundibulum
  • Magnum
  • Isthmus
  • Uterus
  • Cloaca

The Mating Dance

To woo a hen, the rooster usually does a little dance, fluffing his feathers, dropping one wing down, and strutting around her. This not only displays his strength and health but also helps to grab her attention. He'll also make a series of croaking noises to try and win her over. 

The hen now has two options: she can either accept the rooster's advances and allow him to mate with her or reject him. If she accepts, she will squat down, lower her head, and raise her tail feathers. 

If the hen rejects the rooster, she may run away or peck at him. Yes, hens can be picky when it comes to choosing a mate! They look for a rooster with strong features, vibrant feathers, and good health - all signs that he will pass on good genes to their offspring. 

However, even after rejection, the rooster will often chase after the hen until he finally mates with her. 

Tidbitting

Along with the mating dance, roosters may perform a behavior called tidbitting to entice hens. 

Tidbitting is when the rooster picks up and drops bits of food or bugs for one of the hens to eat. He bobs his head up and down and clucks, signaling that he has found a tasty treat. 

The Cloacal Kiss

Once all the rooster's advances are successful, it's time for the 'cloacal kiss' - the actual act of mating and the answer to how does a chicken egg get fertilized.

The rooster will hop onto the hen's back and hold her in place by biting down on the back of her neck. This can sometimes cause some feather loss, but it's all part of the process. There's also a lot of flapping and squawking involved as they adjust themselves into the correct position.

Once the rooster's cloaca makes contact with the hen's, sperm is transferred from the male to the female. The actual fertilization process only takes a few seconds! 

Roosters can mate multiple times a day (as many as 30 times!), and hens typically store sperm for up to 2 weeks. This means they can lay fertile eggs for weeks after mating with a rooster. 

Fun fact: Hens can eject unwanted sperm if she doesn't want that particular rooster to fertilize her eggs!

Do Chickens Need a Rooster To Lay Eggs?

No, chickens don't need a rooster to lay eggs. Hens will lay eggs regardless of whether or not there is a rooster present. However, without a rooster, the eggs will not be fertile and cannot hatch into chicks.

How to Tell if an Egg Is Fertilized

There are two ways to tell if an egg is fertilized. The first way is by cracking the egg open and examining the yolk. If there's a small white spot on the yolk's surface, then you have a fertilized chicken egg. This white spot is called the blastodisc and is where the embryo would form if it were incubated. Now you know the following eggs from that chicken will likely be fertile!

The second way to tell if an egg is fertilized is by candling. Candling involves shining a bright light or egg candler through the egg in a dark room. But there won't be much to see until the embryo grows and develops more. This means you'll need to incubate the egg for a few days before trying this method. 

Candle your egg between days 4 and 7 of incubation. Fertile eggs will show signs of development, including spider-like veins extending from the center of the egg at this stage. If you see this, then your egg is fertilized! 

Fertilized Chicken Egg FAQs