Have you ever collected eggs from your backyard chickens and wondered if they might hatch into adorable fluffy chicks? Or maybe you’re concerned about accidentally eating an egg with a developing embryo inside (yikes!). As someone who’s been raising chickens for years, I can tell you that figuring out whether an egg is fertilized is easier than you might think!
Whether you’re hoping to expand your flock or just curious about the eggs you’re eating, I’ve got you covered with the most reliable methods to check for fertilization. The good news? You don’t need fancy equipment or a degree in poultry science to figure this out!
Understanding Fertilized vs. Unfertilized Eggs
Before we dive into the detection methods, let’s clear up some basics
- Female chickens (hens) lay eggs regularly regardless of whether they’ve mated with a rooster
- Fertilization happens before the egg is formed, when the rooster mates with the hen
- If you don’t have a rooster in your flock, your eggs are definitely unfertilized – no chance of chicks!
- A hen can lay fertilized eggs from 2 days up to 3 weeks after mating with a rooster
One common myth I need to bust right away those little red spots you sometimes see in eggs? Those aren’t baby chicks! They’re just broken blood vessels from the hen’s reproductive tract Both fertilized and unfertilized eggs can have these spots,
Method 1: The Crack and Check Method
The easiest (though obviously destructive) way to check for fertilization is to simply crack the egg open and examine the yolk.
What to Look For:
In every chicken egg, there’s a small white spot on the yolk called the germinal spot. This spot looks different depending on whether the egg is fertilized:
- Unfertilized egg: The spot (called a blastodisc) is small and contains genetic material from only the hen
- Fertilized egg: The spot (called a blastoderm) is larger with a distinctive “bullseye” appearance – it has a clear white edge and contains genetic material from both the hen and rooster
This method is super reliable, but obviously you can’t use it if you actually want to hatch the egg since you’ve, well, cracked it open!
Method 2: Candling – The Non-Destructive Approach
Candling is the most popular method for checking fertilization without damaging the egg. The name comes from the old-school practice of holding eggs up to a candle to see inside, though nowadays we use flashlights or purpose-built egg candlers.
How to Candle an Egg:
- Wait until day 7 of incubation (patience is key here!)
- Find a small, bright flashlight or egg candler
- Go into a dark room (the darker, the better)
- Hold the egg against the light source, larger end up
- Look for specific structures inside the egg
What You’ll See:
- Fertilized egg: Dark lines (blood vessels) spreading throughout the egg, with a small dark shape in the center (the developing embryo)
- Unfertilized egg: Appears clear except for the yolk visible as a dark shadow
I recommend candling on day 7 of incubation because that’s when all viable embryos will be visible. Some may develop quicker and be visible by day 4, but waiting until day 7 ensures you won’t discard potentially fertile eggs too early.
Important candling tips:
- Don’t keep eggs outside the incubator for more than 30 minutes
- Only candle once or twice during development
- Wash your hands before handling eggs
- Return eggs to the incubator immediately after candling
Method 3: The Wait and See Approach
The most passive method is simply to wait the 21 days of incubation and see if chicks hatch. This obviously takes the longest but requires the least intervention from you!
This approach works well if you have a broody hen who’s sitting on eggs. Just let nature take its course.
What a Fertile Egg Looks Like During Development
If you’re candling your eggs, here’s what to expect at different stages:
- Day 1: Looks clear like an infertile egg – can’t tell difference yet
- Days 4-7: Embryo becomes visible with blood vessels extending from center
- Day 14: Embryo much larger, egg appears darker overall when candled
- Day 18: Embryo so large it blocks most light, approaching hatch time
Common Reasons Why Eggs Aren’t Fertile
If you’ve got a rooster but still aren’t getting fertile eggs, here are some possible reasons:
- New rooster – May take about a month to settle in before mating effectively
- Rooster plays favorites – Some roosters mate more with certain hens
- Too many hens – One rooster typically handles 6-16 hens depending on size
- Seasonal changes – Fertility can decrease in extreme weather
- Health issues – Either the rooster or hens might have reproductive problems
Common Myths About Fertilized Eggs
Let me clear up some misconceptions I’ve heard over the years:
-
Myth: Blood spots mean an egg is fertile
Truth: Blood spots can appear in both fertile and infertile eggs -
Myth: Fertilized eggs taste different
Truth: There’s no taste difference between fertilized and unfertilized eggs -
Myth: Fertilized eggs are more nutritious
Truth: Nutritional content is identical in both types of eggs -
Myth: You can tell if an egg is fertile immediately after it’s laid
Truth: You need to wait for development to begin (at least 4 days) before you can tell
Frequently Asked Questions
Are store-bought eggs fertilized?
No! Commercial egg operations don’t keep roosters with their hens, so supermarket eggs are almost never fertilized.
Is it safe to eat fertilized eggs?
Absolutely! A freshly laid fertilized egg that hasn’t been incubated is perfectly safe to eat. The embryo hasn’t started developing yet. Once refrigerated, any potential development stops completely.
How long can fertilized eggs remain viable for hatching?
Fertilized eggs remain viable for about 7-10 days at room temperature. For best hatching rates, collect eggs daily and either start incubating them or store them in a cool place (around 55-60°F) for no more than a week.
Will my eggs hatch if I don’t have an incubator?
Without proper incubation (either from a broody hen or an incubator), fertilized eggs won’t develop. They need consistent temperature (around 99.5°F) and humidity, plus regular turning.
Can fertilized eggs develop in the refrigerator?
Nope! Development stops completely once the egg is chilled in the refrigerator.
Final Thoughts
Telling if a chicken egg is fertilized isn’t complicated once you know what to look for. The most reliable methods are cracking it open to check the germinal disc (if you don’t need to hatch it) or candling after 7 days of incubation.
For those of us raising backyard chickens, understanding egg fertility is both fascinating and practical knowledge. Whether you’re looking to expand your flock or just curious about the miracle of chicken reproduction, these methods will help you know exactly what’s happening inside those eggs!
I hope these tips help you in your chicken-keeping journey! Remember, there’s nothing quite like the excitement of seeing those first signs of life developing inside an egg – it’s one of the many joys of raising chickens that never gets old.
Have you tried checking if your eggs are fertilized? I’d love to hear about your experiences in the comments below!
Do Chickens Need a Rooster to Lay Eggs?
My very first time hatching eggs was 4 years ago. I got these fertilized eggs from Alabama Silkies.
I get this question a few times a year. The answer is no! You don’t need a rooster for a hen to lay an egg. Hens will lay one egg every 24 hours all on their own. However, if you want to hatch out chicks, you do need a rooster.
To produce an egg, chickens need an average of 12-16 hours of light, adequate calcium and a good diet. The whole process of forming an egg inside a hen is absolutely incredible!
How Do Roosters Fertilize Eggs?
When a rooster and a hen engage in mating behavior, the rooster transfers sperm to the hen through a process called “cloacal contact.” This occurs when their cloacas, the common opening for reproductive and digestive tracts, make contact, allowing for the transfer of sperm from the male to the female.
Once inside the hen, the sperm can remain viable for several weeks, ready to fertilize any eggs the hen lays during that time. If an egg has been fertilized, the embryo begins to develop within it.
Its worth noting that the eggs we typically consume are not fertilized (from the grocery store or your coop as long as you dont have a rooster). However, its also perfectly safe to eat a fertilized egg, as long as theyre fresh and havent been incubated. In fact, fertilized eggs look and taste just like unfertilized ones (see the comparison below).