How to Tell if a Chicken Egg is Fertilized

How do I know if my chicken egg is fertilized? Learning how to tell if a chicken egg is fertile is an important skill to have if you want to hatch out your own chicks or sell fertile eggs from your flock of chickens.

Just because a rooster is in with a flock of hens doesn’t always mean the chickens’ eggs will be fertile!

We love to hatch eggs in our incubator and my kids sell fertile eggs. But to do either of these, we need more reassurance that the eggs from our hens are consistently fertile.

Why do I need to know if my chicken egg is fertilized?

If you’re planning to hatch chicks in an incubator or sell fertile eggs, you need to know if the hens are consistently laying fertile eggs.

Last year we had a bad experience buying fertile eggs from a local gal. She had an adorable flock of bantam chickens and my kids wanted to hatch out their own little flock of bantams to add to their breeding flocks.

We saw a bantam rooster in with the bantam hens so didn’t think twice when spending a chunk of money on some of her fertile eggs.

Unfortunately only one out of the eight hatched while other fertile eggs from our own hens had no issues with hatching so we could rule out incorrect hatch conditions as a cause.

My kids were devastated. I was upset since we had wasted some hard earned cash on these fertile eggs.

I called up the gal I bought the fertile eggs from to let her know what happened.

She then confessed that she had gotten a new rooster the week before and he hadn’t been in with the hens for very long so the eggs were probably not fertilized. I’ve read that it can take a new rooster up to a month to settle in with a new flock of hens and start mating.

What an unfortunate experience and a waste of money!

As a family that sells fertile eggs, I strive to ensure to the best of our abilities that the eggs we sell are fertilized. We never want anyone else to have the type of unfortunate experience we had!

How Long Will a Hen Lay Fertilized Eggs?

A sexually mature rooster in with a flock of hens will likely mate with all the hens at least once over the course of a week (likely a lot more than that!) After mating, the rooster’s sperm is stored in the hen’s oviduct.

Hens should start laying fertile eggs 24-48 hours after mating with a rooster. Fertility from mating lasts approximately 10-14 days.

Can you Tell the Difference Between a Fertilized and Unfertilized Egg?

When looking at the exterior shell of a chicken egg, there is no way to tell if the egg is fertilized or unfertilized. Just like all eggs look the same on the inside regardless of the exterior shell color.

If we could tell the difference, that would be so much easier for those  of us who hatch chicks and sell fertile eggs!

Luckily there are two different ways to tell if a chicken egg is fertilized or unfertilized.

One method involves cracking the egg open which works if you’re not planning to incubate the eggs.

The second method involves using a flashlight to take a peek inside the egg after it starts incubating.

How to Tell if a Chicken Egg is Fertile When Cracking it Open

So what do we do to try and verify if our hens are consistently laying fertile eggs? I assess every chicken egg I crack open from our flock to determine if it’s fertile.

Since fertilized and unfertilized eggs look exactly the same on the outside of the shell, you have to look for a specific mark on the egg yolk to verify if it’s fertile.

Every time I crack open an egg from one of our hens, I carefully look for “the spot”. By “the spot”, I mean the small white dot on the yolk called a germinal disk

I look to see if the spot has concentric circles around it and looks a little bit like a bullseye.  The presence of the “bullseye” tells you that your chicken egg is fertile.

A non-fertile chicken egg will have just the tiny white dot and no concentric rings around it like the fertile egg.

If you’re curious to learn more, here’s a great article about egg anatomy and what’s inside the egg shell.

How to use a flashlight to tell if a chicken egg is fertilized without cracking it open

Obviously if you’re wanting to incubate eggs, you can’t crack them open to verify if they are fertile. Once we know that our hens are consistently laying fertile eggs, I start collecting them for the incubator.

Using a flashlight to take a look inside the egg after it starts to incubate is called candling. This method has been around for a very long time and is so fascinating to do!

You can use a regular flashlight, which we tried our first year incubating eggs, but found that investing in a specific egg candling flashlight is a lot easier to use.

Using a specific egg candling flashlight gives you better candling results. This is due to the way the flashlight cups the egg to direct the light inside. This helps to improve how well you can see inside the egg to see if it’s fertile without cracking it open.

When to candle eggs and what to look for

Eggs need to be incubated a bit before candling to check for fertility. When incubating eggs, we candle the eggs around day 7 and again around day 14 to ensure growth is still occurring.

There are very specific things to look for inside the egg at certain stages of development.

When candling eggs to look for fertility, make sure the room is dark so you can see inside the egg better.

Carefully hold the egg candling flashlight under the rounded end of the egg which is where the air sac is located inside.

How do you know if a chicken egg is fertilized in the incubator

When candling an egg around day 7, you need to look for the dark spider web type lines through the egg leading to a dark spot, which is the embryo. The darker the egg shell, the harder it is to clearly see this growth.

If the egg is clear and there is an absence of this dark spot and lines, it means that the egg may not be fertile.

I mark these eggs and candle them again on day 10. If there is still no sign of fertilization then I remove them from the incubator.

How to tell if an egg has a chick in it

When candling eggs around day 14, you will be able to see a lot more growth of the chick inside the egg. If you still see the same small dark spot and lines like you saw on day 7, then the embryo is no longer growing and the egg needs to be removed.

If you see a red ring around the inside of the egg when candling, this means that for some reason the chick had started developing and then died. These eggs are no longer developing and need to be removed from the incubator.

By day 14 you can usually see the shape of the chick inside the egg instead of a dark spot of the embryo. It’s especially exciting when you can make out the shape of the head and even a beak!

Here’s a post with more detailed photos of chicken embryo development  to give you more insight into what exactly is occurring inside the fertilized egg at every stage of development.

Can you eat fertilized chicken eggs?

Fertilized chicken eggs that have never been incubated are perfectly safe to eat just like non-fertilized eggs.

Eggs need several days of the perfect warm temperature around 99.5 degrees in an incubator or under a broody hen to start to develop.

If your eggs are kept in a cool spot or refrigerator, the fertile egg won’t start to develop.

Fertile chicken eggs taste the same as unfertilized eggs and have the same nutritional value.

If you didn’t look for the bullseye spot to verify the egg is fertile, you wouldn’t even know the difference between eating a fertile and unfertilized egg!

The results of our recent fertilized eggs test

We are hoping to run our incubator and hatch chicks later this month so for the last couple weeks I’ve been checking every single egg from our hens that we crack open.

Sometimes when we crack the eggs open, the yolk lands in the bowl where I can’t see the germinal disk. In this case, I carefully scoop it out with a spoon and try to turn it over until I can see “the spot” to verify if the egg is fertilized or unfertilized.

So far every egg I’ve checked has the tell tale “bullseye” mark showing it is fertilized. I guess our roosters are doing their jobs well!