Why Do Ostriches Lay Unfertilized Eggs? How Often?

Seeing ostriches in the wild is fascinating. My first trip to South Africa was a treat for me especially because of these tall birds. I remember the scene vividly. We were on a safari in the African Savannah and came across a female ostrich and her nest! 

Intro Video - Backtobirds
Intro Video - Backtobirds

The female seemed to sense a threat and got up from her nest and came towards us threateningly. This gave us the perfect opportunity to view her view. If you are a birdwatcher, then you know how rare and special such moments are in the wild. 

The nest seemed to be a shallow hole dug in the ground and it was filled with about 15 large eggs! I was ecstatic when I imagined 15 little ostrich birds coming into the world.

I asked the ranger how many eggs usually hatched successfully and he told me that it could not be determined. If the mother was young, there was a high chance that her eggs would be unfertilized. 

When I read about this, I found that it was indeed true!

Why do birds lay unfertilized eggs?

All birds lay eggs to reproduce. These eggs are fertilized inside the female’s body, unlike the external fertilization in Amphibians. This means that the eggs are fertilized before the female bird lays them. 

Just like humans, female birds have an ovulation cycle. This means that the ovary produces a sort of unshelled egg. Once this egg is released from the ovary, it can be fertilized by the male sperm at this stage.

The egg then, regardless of whether it is fertilized or not, passes through stages in the female body which gives it the hard covering of calcium carbonate (CaCO3) i.e. the shell of the egg. The female then lays the egg/s and incubates them.  

If there is no male present or if the sperm are unable to fertilize the egg, the female still lays the egg/s and incubates them. This is how we get unfertilized eggs.

Related Read: What Birds lay Blue Eggs? | Identify Blue Egg Species of Birds

Can ostriches lay unfertilized eggs?

All bird species lay unfertilized eggs at some time or the other. Yes, ostriches can lay unfertilized eggs. Since we have understood why birds lay unfertilized eggs, we know that the reason remains the same for ostriches too. 

It has been observed that larger bird species take more time to lay fertilized eggs. This means that the early eggs that large female birds lay are often unfertilized. It takes a while to get it ‘right’.

Also, since birds in the wild have to fight to get food, nutrition, and safety in the wild, it is rare for them to lay unfertilized eggs. Laying eggs takes a lot of time and nutrition from the female birds. So, it is not feasible for birds to lay eggs that won’t even hatch with their young. 

Another reason for it to be a rare occurrence is that there is no dearth of males in the wild who wish to mate with a female. Hence, in most cases, the female does mate with the male before she lays the eggs.

How often do ostriches lay eggs?

Ostriches do not lay eggs all year round as hens do. They have a specific breeding season. This season falls in June/July. During this time, an ostrich lays one egg approximately every second day. In total, the female lays around 12-15 eggs each season.

Once the ostrich has laid enough eggs, a male-female pair takes turns to incubate them. Interestingly, the ostrich may have eggs from different males within the same nest.

Related Read: What Not To Feed Wild Birds? ( Harmful Foods For Wild Birds )

How can you tell if an ostrich egg is fertilized?

It is surprisingly easy to tell whether or not an ostrich egg is fertilized.

Take the ostrich to a dark area. Make sure you carry a flashlight. Even your phone’s flashlight will work. 

Since an eggshell is porous, you can actually see inside it. Switch on the light and place it very close to the egg. If you see a black spot inside the eggs, it indicates an embryo. This means the egg is fertilized. Unfertile eggs do not have an embryo inside them.  

How are unfertile ostrich eggs used?

The importance and uses of ostrich eggs can be seen from early history. These eggshells have long been used to make bowls and containers to carry food and water.

The unfertilized eggs are also often used for decorative purposes. They are painted, used in jewelry pieces and for mosaic work too.

Related Read: What Are The Longest Lived Birds ( Lifespan Of Birds List, Types, Care )

Related Questions:

How big are ostrich eggs?

Ostrich eggs are the biggest eggs of any living bird. They measure around 17-19 cm in length, 14-15 cm in width, and can weigh up to almost 2 kgs!

However, it is interesting to note that these eggs, despite being the largest, are the smallest in relation to any bird. Ostrich eggs only make up about 1 percent of the bodyweight of a female ostrich.

Do people eat ostrich eggs?

People can eat ostrich eggs but usually don’t. Ostrich eggs are said to taste similar to chicken eggs, except that they are more rich and buttery. However, they are not eaten on a regular basis solely because these eggs are too big and most people don’t need to eat so much.


Ostriches, like all other birds, do lay unfertilized eggs sometimes. We don’t have an exact number but it is assumed that the number may be around 10% of all eggs laid. 

Of course, this depends on a variety of factors including availability of a safe nest, mating process, climate, and age of the female bird. Unfertilized eggs are generally not eaten but are used for a variety of decorative purposes.

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