Why Do Birds Lay Unfertilized Eggs?

The reason that I discovered that my Bare-Eyed Cockatoo was actually a female (11 years after I got her) was that she suddenly started laying eggs. In this post let’s look at the question of why do birds lay unfertilized eggs?

Why Do Birds Lay Unfertilized Eggs?

why do birds lay unfertilized eggs

It can be quite surprising when you find an egg at the bottom of your birdcage, and the bird in question doesn’t even have a mate.

In cases like mine, my parrot was sold to me as a male, so imagine my shock when I discovered that it was actually a female 11 years down the line.

Unfortunately, it is not always possible to accurately sex a parrot, and people rely on methods like looking at behavior, or at their bone structure. So when and if your bird does suddenly lay an egg, then you know without a doubt that it is female.

There are several reasons that birds lay unfertilized eggs without a mate. Cockatiels for example are notorious egg layers.

In the wild, birds are seasonally breeding and egg-laying and these activities normally occur during the spring and summer months. It is during these months that breeding hormones are stimulated more. The reasons are because of the following:

  • increased daylight hours
  • the warmer climate which is conducive to breeding
  • more rain which is great for bathing and food is more readily available
  • a variety of insects and plants can be found during the summer months for food. During the winter months, a bird in the wild would mainly live on seeds.

Unlike wild birds, your pet birds actually have the above ideal breeding conditions all year long. When something stimulates your bird’s breeding hormones she will display breeding behavior and start to lay eggs. Males on the other hand will show more aggression than normal.

Here are some more things that can stimulate the breeding hormones:

  • Water is plentiful allowing birds to bathe indoors all year long.
  • A warm indoor environment is ideal for breeding any time of the year.
  • The bird has bonded with a toy or human and perceives that object or person as her mate.
  • The bird has paper, wood, or straw in its cage which it can shred as nesting material.
  • An abundance of foods suddenly, including soft foods.
  • Petting a bird on the back, under the wings, or on the stomach can stimulate its breeding hormones.

Your bird could lay a single egg or even one every two days. Sometimes if you remove the egg, it will lay another to replace it.

How Do You Know Your Bird Is Ready To Lay Eggs?

The bird will feel heavier, weigh more and their lower abdomen near their vent will feel firmer and look larger. The hen will also drink a lot more water than normal.

why do birds lay unfertilized eggsShe will also start to chew up things in her cage to make a nest, like wood or paper. They will suddenly become protective of their cages and could back into a corner on the floor making chirping sounds.

Prior to and during the egg-laying process the droppings will be loose, large, and have an odor. If there is a lack of droppings, it could be a case of egg binding.

The experts warn not to remove the eggs out of the cage in the case of cockatiels, as they will just carry on laying. However, I remove the eggs that my bare-eyed cockatoo lays, as she seems to only lay two and then give up on the idea.

It is considered safe for your bird to lay eggs up to twice a year, but if your bird becomes a chronic egg layer, it could become life-threatening.

In this case, you would need to remove any stimulus in the cage that could be causing the egg-laying such as nesting material, mirrors, water baths, etc.

So hope that this article has shed some light on the subject of why do birds ly unfertilized eggs for you.


  1. Wow, I wasn´t aware that birds could lay unfertilized eggs. I thought it was only a hen´s thing, but makes totally sense now. I did have a few birds when I was a kid, and I was always checking if there were any eggs. Thing is I was never able to identify if they were both males (think they might have been). It´s amazing how nature can teach us so much things about it, and next time I have a parrot or a bird per se, will totally check it´s behaviour. 

    1. I also thought it was only chickens that did this, but when I happened to me I started to explore the idea further and discovered it can happen with all birds.

  2. Your article on birds laying eggs was indeed extremely helpful. I imagine this phenomenon also applied to chickens. Maybe you can answer this. Are the eggs we buy in supermarkets created in this way? I always wondered if the hens needed a mate to lay eggs. I was totally surprised to learn that a mate was not necessary for the hen to lay eggs. 

    When I see birds in cages now I will look for clues to see if they are potential egg layers. 



    1. Hens are kept in ideal conditions, that are sometimes even cruel to enable them to lay eggs. These include keeping the lights on all night so that they think that it is day time all the time. They also don’t need a mate to lay eggs, and most of the eggs you buy in the supermarket are not fertilized.

  3. Very interesting information about birds laying unfertilized eggs.  Your blog post made me laugh as well, you thought you had a male and found a egg in your bird cage. I learned a great deal from your post, its amazing how climate can effect the breeding process of birds. I have always wondered about the bird breeding process. Now I know thanks to you. 

    This makes sense when you think of chickens too. They just carry on laying and laying once their eggs are taken away.

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