finch nest

Egg candling and incubation. How to check bird’s eggs.

As mentioned in a previous article, the hen will sit on the nest during the egg incubation period and she will leave the nest a couple of times a day for various reasons. The male will not sit on the nest but he will feed the hen and help to rear youngsters. Egg candling technique is mostly used to save precious time if the eggs are infertile.

Egg candling and incubation

The eggs will hatch in 13 to 15 days depending on the humidity and temperature. The hen will sit on the eggs for the entire incubation period and until the chicks will be old enough to maintain their body temperature. This is at around 10 days old.

Candling eggs is normally done after the 4th day of incubation. This will tell the breeder if the eggs are fertile or not. If the eggs are not fertile, the nest can be removed for few days and then reintroduced so that the bird can start building again.

The candling can be done with a mobile phone and a low source of light. Place the egg on the torch and you will find out if it is fertile or not. The best practice would be to use a lighting device that will not require removing the eggs from the nest (for example a light pen).

The difference between a fertile and an infertile egg is very simple:

Infertile egg: this egg will appear very clear when candled. It will be similar to a freshly laid egg.

Fertile eggs: this egg will show a map of red veins and if you look closer you can even see the heartbeat. There will be a huge difference between a fertile and infertile egg.

Egg candling
Egg incubation
Infertile egg
Egg candling
Egg incubation
Fertile egg

Checking the eggs from the 4th day of incubation onwards can sometimes save your breeding season. First will save valuable days by removing the nest of infertile eggs and if it happens again, it should be the time to ask yourself questions like:

Is any of the birds too old?

A young bird will have more chances to have fertile eggs than an old one. Best results will come from birds in their first 3 years of life. The first 10 to 12 months of its life will reach breeding age and the next 3 years will be in the best breeding shape. For example, a bird born in 2021 will reach maturity by 2022 which will be their first year to breed and then 2023 and 2024 will be their best breeding years. The birds will lay fertile eggs after that too, only that the chances will decrease as it gets older.

Are the birds healthy?

An unhealthy bird will always cause problems. They Will either lay eggs that are infertile or will not sit on the eggs and so they will get cold. Also, they could lay eggs and sit on them but will not feed the chicks.

Are the birds too fat?

Blow the feathers on their belly and pay close attention to the color of their skin. This should be done at least a month before breeding season. If the skin is red, then the bird should be fine for breeding. If the skin looks very yellow then, the bird could be too fat and this will have a bad effect during the breeding season.

Red eye female canary 2020
Fat bird
Red eye male canary 2019
Fat bird
Red eye female lutino greenfinch 2020
Perfect condition

There are lots more reasons why a bird is having difficult time breeding but I will write about this in a different article.

It is recommended to take notes during the breeding season. Those notes should include the day the first and last egg was laid, the day the eggs should hatch and also the day when the chicks should be separated from their parents.

Make sure that the birds will have lots of soft food, vegetables and fruits a couple of days before hatching. This will help the birds to feed their chicks easier and faster.

Soft food
Soaked seed with mealworm, egg food and peas
Dandelion full plant
Dandelion heads

Humidity is very important when the eggs are due to hatch. The hen will take a quick bath and fly back into her nest. The wet feathers will soften the eggshell a little bit and this helps the newborn to break his way out.


A female bird can lay eggs without being together with a male. Those eggs will never be fertile.

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  1. Pingback: Hatchlings – Feeding hatchlings| Bird Room Guide

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