How to Tell If a Duck Egg Is Fertile [3 Easy Ways!]

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How can you tell if your duck eggs are fertile? Consider the following advice from our Indian runner ducks! Let me explain.

Our Indian runner ducks are laying once again! But, they have a somewhat haphazard approach to egg production. When it comes to mating, their enthusiasm knows no bounds.

Given how many sexual shenanigans we witness in our duck enclosure, our flock should have tripled or quadrupled by now. But no, our ducks never seem to get broody!

Nevertheless, it’s fair to say that every egg they lay should be fertile.

But – Indian runner ducks are still notoriously difficult to breed because they don’t have motherly instincts. We have several broody chickens. So, we could try incubating the eggs that way, even if the poor hen would be teeter-tottering on her clutch of jumbo eggs!

There’s no point in getting a chicken to sit on unfertile duck eggs, so I started wondering how to figure out if the eggs were fertile.

According to my research, there are three ways to tell if a duck egg fertilizes.

Although, the third duck egg fertility test isn’t very scientific and sounds a little dubious. Other (seemingly redundant) methods involve examining the duck egg for cracks and waiting for any movement.

I don’t think it requires (or deserves) much more of an explanation than that!

However, we want to discuss three other methods for checking duck egg fertilization.

Read More – When Do Ducks Start Laying Eggs? Read Our Timeline!

How to Tell If a Duck Egg Is Fertile (3 Methods)

Caring for baby duck eggs takes a lot of work. For you – and the mother ducks!

It’s much more work if you spend all of that time nurturing an unfertilized egg!

There are only three methods we know of to help determine the status of your duck egg fertilization.

They are as follows:

  1. Candling duck eggs. This is, by far, our preferred method of checking whether the eggs are fertile. Candling basically means shining a bright light onto the egg, so you can see what’s happening inside. We’ll go into more detail below.
  2. Observe the germinal disc of the duck egg. This method means you need to crack the egg to see what’s happening – not recommended if you’d like the egg to hatch! Futher information below!
  3. The float test. This test is, in our opinion, outdated. Use the candling test is possible!
two adult ducks protect eggs straw nest
Here you can see two adult ducks watching over and protecting their eggs. The ducks and eggs are safe in their straw nest. But are these duck eggs fertilized? It’s tough to see without going in for a closer look!

Method 1 – Egg Candling

egg candling embryo development
Egg candling allows you to see the contents inside the egg. Looking at the opacity, shape, and egg contents can help determine the duck egg’s fertility status.

Egg candling is our preferred method to see if your duck egg fertilized successfully or not!

Egg candling is modern, safe, and almost guaranteed to work. It’s the best method to see if your duck eggs are fertilized – or not.

Egg candling has nothing to do with creating a romantic atmosphere using scented candles and soothing music but everything to do with shining a bright light onto an egg to see what’s happening inside. 

The easiest way of candling eggs is with a customized egg candler light. These can either be placed on a flat surface or held in hand. (The photo above depicts a commercial egg candler and incubator.)

If you hold an egg up to the light, you’ll be able to see through the porous shell into the egg itself. A couple of days after fertilization, a white circle appears in the center of the egg yolk.

After about a week, this will develop into a dark spot with spider-like veins stretching out from it like tentacles. 

After a couple of weeks, the dark spot will grow and fill the egg. The blood vessels will also increase in size and become more distinct. 

Egg candling enables you to distinguish between non-fertile and fertile eggs and ascertain when they contain dead embryos.

Eggs with dead embryos can be removed from the incubator or nest and discarded, allowing you or your broody duck to focus on the live ones.

If you candle a non-fertile egg, all you’ll see inside is the shadow of the yellow yolk without any white circle, dark spot, or veins. My farming colleagues call this egg a clear egg!

Embryo deaths are relatively common and can occur at any time during the incubation process. If an embryo dies within the first few days, a thin ring will appear around the inside of the egg.

Embryo deaths that occur within the first week are known as quitters. In these eggs, the embryo will still be visible. But, the egg embryo takes on a cloudy appearance and moves around as you rotate the egg.

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02/17/2024 05:28 am GMT

Method 2 – Observing the Germinal Disc

duck egg germinal spot fertilization
Fertilized duck egg yolks have a large bullseye-shaped germinal spot or germinal disk. Non-fertilized duck egg yolks will have a germinal disk with a much smaller circumference.

Another easy way to tell if a duck egg is fertile is to crack it open into your frying pan. But, in doing so, you instantly eliminate any chance of a successful hatch.

If you want to keep your baby duck embryos alive, we recommend using the egg candling method. By far!

But – we want to share the rationale behind this method, nevertheless.

After cracking open a duck egg (or chicken egg) – you can look for the egg’s germ spot. The germ spot looks like a white spot on the egg yolk.

Non-fertilized eggs will appear as a small and solid white blotch. Fertilized eggs have a wider germinal spot. (The fertilized germinal spot in the yolk contains male and female cells. And – they combine and get larger.)

The germinal spots also resemble a bullseye design after egg fertilization.

Read More – Raising Ducks 101! Our Complete DIY Guide!

Method 3 – The Float Test

baby duckling hatching out of her egg
This duck egg fertilized and hatched successfully. Help us welcome a new baby duck into the world! She doesn’t need food yet. But after 24-48 hours, she will get hungry. Prepare some water and feed!

Warning – the float test is risky and outdated! And we don’t recommend it!

However, a handful of our homesteading colleagues swear that it works. So, we decided to share.

The old-fashioned egg float test helps establish the freshness of eggs. Old rotten eggs float – and fresh eggs usually sink! But – others consider a similar idea on the 23rd or 24th day of incubation to verify a duck egg’s validity.

It’s an outdated method – and I don’t like it that much because I don’t fancy the idea of submerging my baby duck eggs into the water!

(Even for a moment.)

Before performing a float test, examine the egg to double-check for cracks. If the embryo is still alive – but the egg cracked, performing the float test would cause it to drown. (That’s why I recommend against this method.)

Fill a container with lukewarm water, making sure it’s deep enough to cover the egg with a couple of centimeters of water to spare. The ideal temperature is around 95 – 100℉. That’s around the same temperature for proofing yeast when baking bread. 

Wait for the water to stop moving, and then gently lower the egg into the water.

  • If the egg sinks to the bottom and doesn’t move, the egg was potentially infertile from the start of the incubation period.

If the egg floats, carefully watch it and establish its floating pattern.

  • If the narrow end of the egg is pointing straight down and doesn’t move, the egg may contain a dead embryo. 
  • If, however, the egg floats at a more horizontal angle, the hatchling may still be alive. If the egg starts bobbing around of its own accord, there’s a baby duck inside waiting to hatch!

If that’s the case, time to celebrate. Your baby duck seems healthy – and it wants to hatch!

Dry off the eggs and return them to the egg or incubator to complete the incubation process!

(Again – we don’t recommend using the float test for duck egg fertility testing. Egg candling is safe, effective, and more humane.)

Read More – Should You Keep Ducks for Pets? 7 Pros and Cons!

Duck Egg FAQs – Hatching the Answers to Duck Breeding Questions!

adorable baby ducklings hatched fluffy
Look at these adorable baby ducklings! I don’t think mother nature has many backyard fowl as lovely as these! It looks like they’re trying to find mother duck. Or – maybe lunch!

We know that raising ducks and ducklings is a handful!

But no worries – we put together a list of the most common duck breeding and duck egg fertilization FAQs.

Hopefully – you find them useful.

How Long Are Duck Eggs Fertile?

Fertile eggs from chickens or ducks will stay viable for approximately seven days after laying. If they’re left much longer, their fertility will start to decline, so you need to get them into an incubator or under a broody duck swiftly. Handling, sanitation, and environmental factors may also contribute to the length of fertility.

Will Ducks Sit on Unfertilized Eggs?

A broody duck will sit on almost anything, including infertile eggs! As a broody hen or duck will stop eating and laying eggs, this type of wishful thinking isn’t particularly useful or desirable. Your broody flock members may prefer staying in their nest or enclosure during broodiness, only to leave once or twice per day for food or water.

Read more about why chickens stop laying eggs here: https://www.outdoorhappens.com/reasons-why-chickens-stop-laying-eggs

What Do I Do If I Find a Duck Egg?

If you find a duck egg in the wild or one that looks abandoned in a random corner of your homestead, chances are, it’s infertile.

If you find a whole clutch of eggs that are still warm, however, there’s a good chance they contain baby ducks. Leaving them in place gives them a good chance of survival. But, if you want to make sure, you could use one of the three methods described above to evaluate their validity.

If you are confident they’re viable and are desperate for cute, fluffy baby ducklings, then pop them in an incubator and hatch them!

mother duck protecting duck eggs
Here’s a lovely mother duck protecting and warming her duck eggs. Duck eggs usually take around 25 to 30 days to hatch. Many farmers swear that broody chickens will hatch duck eggs just as well as broody ducks!


It’s not easy to tell if a duck egg is fertile just by looking at it – and cracking it will end the embryo’s life (and potentially put you off your breakfast).

Duck egg candling is the best, safest, and most humane way to test duck egg fertility. Although – the float test may also work effectively later in the incubation process.

Whichever method you choose, we wish you all the best and hope you’ll soon have a clutch of ducklings to worry about and marvel over.

Also – let us know your experience with baby ducks!

Do you have any tips for the healthy fertilization of ducklings and their eggs?

Or do you have photos of your baby ducklings you want to share?

We love to hear your thoughts!

Thanks again for reading!

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02/17/2024 07:32 am GMT

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