Ever cracked open an egg and wondered if it could have become a fluffy little chick? Whether you’re raising backyard chickens for the first time or just curious about the eggs you eat, knowing how to identify a fertilized egg is a valuable skill I’ve been raising chickens for years now, and one of the most common questions I get from visitors to my small farm is “How do you know if a chicken egg is fertilized?”
Let me walk you through everything you need to know about fertilized eggs from identification methods to common myths. This guide will make you an expert in no time!
The Basics: Do You Need a Rooster for Fertilized Eggs?
Before diving into identification methods, let’s clear up a common misconception:
No hens do NOT need a rooster to lay eggs! Hens will happily lay eggs every 24-26 hours regardless of whether a rooster is present. However without a rooster, these eggs are infertile and will never develop into chicks.
If you buy eggs from a commercial farm or supermarket, you can be 100% certain they’re not fertilized. As Dr. Richard Fulton, a poultry veterinarian with over 30 years of experience, explains: “Eggs produced by commercial farms are never fertile because the hens are never with a male.”
How Do Roosters Fertilize Eggs?
When a rooster and hen mate, they transfer sperm through a process called “cloacal contact.” The cloaca is the common opening for both reproductive and digestive tracts. Once the rooster’s sperm enters the hen, it can remain viable for several weeks, ready to fertilize any eggs the hen produces during that time.
The important thing to remember is that fertilization happens inside the hen before the shell forms around the egg. The rooster doesn’t fertilize eggs after they’re laid!
3 Reliable Methods to Identify a Fertilized Egg
Let’s get to the practical part – how can you actually tell if an egg is fertilized? Here are three effective methods:
Method 1: Check the Germinal Disc (Crack It Open)
This is the easiest and most reliable method, but obviously only works if you don’t mind cracking the egg open:
- Crack the egg onto a plate
- Look at the yolk
- Find the germinal disc (a small white spot on the yolk)
In an unfertilized egg: The germinal disc (also called a blastodisc) appears as a small, solid white dot on the yolk.
In a fertilized egg: The germinal disc (now called a blastoderm) looks like a “bullseye” – a white ring with a clear center. This distinctive “donut” appearance is the most reliable indicator of fertilization.
This bullseye formation happens because the disc contains merged male and female cells that will eventually develop into a chick embryo if properly incubated.
Method 2: Candling (For Eggs You Want to Hatch)
If you want to check for fertilization without cracking the egg (like when you’re planning to hatch chicks), candling is your best option:
What you’ll need:
- A small, bright flashlight
- A dark room
- The egg you want to check
Steps:
- Wait until day 7 of incubation (candling too early won’t show development)
- Go into a dark room
- Hold the egg against the light source
- Look for signs of development
In a fertilized egg at day 7: You’ll see a network of blood vessels spreading from a small dark spot (the developing embryo). These appear as dark lines branching through the egg.
In an unfertilized egg: The egg will look clear with just the yolk visible as a floating shadow.
Candling gets its name from the original practice of using candles as the light source, though modern flashlights work much better!
Method 3: Look for Development Over Time
If you’re incubating eggs, tracking their development can reveal if they’re fertilized:
- Day 4-7: Blood vessels become visible when candling
- Day 14: The embryo is significantly larger, blocking much of the light
- Day 18: The egg appears almost completely dark except for the air sac
If no development occurs by day 7, the egg is either infertile or the embryo died very early.
Common Myths About Fertilized Eggs Debunked
There are lots of misconceptions about fertilized eggs. Let’s set the record straight:
Myth 1: Blood spots mean an egg is fertilized.
Truth: Blood spots have nothing to do with fertilization. They’re simply caused by a burst blood vessel in the hen’s reproductive tract.
Myth 2: Fertilized eggs taste different.
Truth: There is absolutely no taste difference between fertilized and unfertilized eggs. If you made two omelets – one with fertile eggs and one with infertile eggs – you couldn’t tell them apart.
Myth 3: Fertilized eggs are more nutritious.
Truth: A hen’s body provides the same nutrients to all eggs, regardless of fertilization status. There’s no nutritional advantage to eating fertilized eggs.
Myth 4: You can tell if an egg is fertilized just by looking at the shell.
Truth: The eggshell gives no clues about fertilization. It doesn’t change color, shape, or thickness if the egg is fertilized.
Is It Safe to Eat Fertilized Eggs?
Yes! A freshly laid fertilized egg is perfectly safe and tasty to eat. Without proper incubation conditions (consistent warmth of about 100°F for several days), the fertilized egg won’t develop into a chick.
The embryo development only begins when incubation starts, so a fertilized egg collected promptly from the nest box is essentially the same as an unfertilized egg for cooking purposes.
Why Might Your Eggs Not Be Fertilized?
If you have a rooster but aren’t getting fertilized eggs, several factors could be at play:
- New rooster: It can take up to a month for a new rooster to adjust and begin mating regularly
- Favorite hen syndrome: Some roosters pick favorites and don’t mate with all hens equally
- Too many hens: One rooster can typically handle between 6-16 hens depending on his size and vigor
- Health issues: An unhealthy rooster may not mate successfully
- Seasonal factors: Fertility can decrease during extreme weather or molting periods
When Candling Eggs: A Timeline Guide
If you’re incubating eggs for hatching, here’s what to expect during candling:
| Day | What You’ll See | What It Means |
|---|---|---|
| Day 1 | Clear egg with visible yolk | Too early to determine fertility |
| Day 7 | Blood vessels and small embryo | Fertile egg developing normally |
| Day 14 | Larger dark area, more defined vessels | Continued normal development |
| Day 18 | Almost completely dark except air sac | Chick nearly ready to hatch |
If you see a blood ring (a circular red line) at any point, this indicates a fertile egg where the embryo has died.
Tips for Successful Egg Candling
• Don’t keep eggs out of the incubator for more than 30 minutes
• Wash your hands before handling eggs to prevent contamination
• Candle only 1-2 times during development to minimize disruption
• Mark any questionable eggs and recheck them a few days later
• Use a dedicated egg candler for best results (though a small flashlight works too)
My Personal Experience with Fertilized Eggs
When I first started keeping chickens, I was so excited when I found my first fertilized egg! I remember cracking it open for breakfast and spotting that distinctive bullseye pattern on the yolk. Even though I knew it was perfectly safe to eat, there was something oddly special about knowing this egg had the potential to become a chick.
Now that I’ve been raising chickens for years, I can spot a fertilized egg in seconds. I’ve even candled eggs with my kids as a fun science project, showing them the tiny developing embryos and blood vessels. It’s a magical process that never gets old!
Final Thoughts
Whether you’re planning to hatch chicks or just curious about the eggs you collect, knowing how to identify fertilized eggs is a valuable skill for any chicken keeper. The bullseye method is by far the easiest way to check, but candling provides a fascinating window into the development process if you’re planning to hatch.
Remember, there’s nothing special or different about eating fertilized eggs – they’re just as safe and tasty as unfertilized ones. And if you’re trying to hatch chicks, patience and careful observation during candling will help ensure success.
Do you have experience identifying fertilized eggs? What method works best for you? I’d love to hear about your chicken-keeping adventures in the comments below!
“How Can I Tell If My Chicken Eggs Are Fertilized Without Cracking Them?”
I recently got that question from a reader who wanted to hatch some of his chickens eggs. He has 8 chickens and 1 rooster. He currently has collected about 20 eggs and is wanting to know if they are fertile, so that he can put them in an incubator.
While I am not allowed to have roosters due to my neighborhood covenants, I have always kind of wondered if I would get a fertilized egg before I get rid of them.
We order chicks and usually get a rooster or two out of the bunch. We get rid of the rooster pretty soon after we know that it is in fact a rooster, though.
How Can I Tell If My Chicken Eggs Are Fertilized Without Cracking Them?
So, first a little talk about the birds and the bees {only, in this case, it really only involves two birds}. In order for an egg to become fertilized, the rooster and the hen have to have mated prior to the formation of the egg. If this happens, the hen will lay a fertilized egg.
This probably goes without saying, but if you don’t have a rooster, you will not have any fertilized eggs. Ever. A hen can lay fertilized eggs from anywhere to 2 days after mating to 3 weeks after mating with the rooster.
The oldest and easiest way to tell if an egg is fertilized is called candling the egg. It is literally holding the egg up to a lit candle {not to warm it, but in order to see inside of the egg}.
How to tell if your chicken eggs are fertile
FAQ
How to tell if a chicken egg is fertilized without cracking it?
To determine if a chicken egg is fertilized without cracking it, you must candle it after about four to seven days of incubation in a dark room, using a bright light source like a flashlight. A fertilized egg will reveal a dark, circular spot with a network of “spider-web” like blood vessels radiating from it. An infertile egg will appear clear, with only the yolk visible, and no signs of development.
How can you tell if an egg is fertilized?
How do farmers know if an egg is fertilised?
Another method to tell if an egg is fertilized is called “candling.” Use a bright light source in a dark room, hold the egg against the light and observe the interior. Fertilized eggs display intricate spider-like veins and a dark area indicating embryo development, while unfertilized eggs appear uniformly translucent.
How soon can you tell if a chicken egg has been fertilized?
You can tell if a chicken egg is fertilized and beginning to develop by candling it with a bright light after about 4-7 days of incubation. A fertilized egg will show a developing embryo as a dark spot with a network of red veins spreading outward. If you see a clear egg with just the yolk visible, it is unfertilized.