Incubation: How To Tell If An Egg Is Fertile Or Infertile

Photo of Kassandra Smith

Kassandra Smith

Senior Editor • Backyard Chicken Coops

Last Updated: 23 January 2020

Not sure whether your eggs are fertile? There are a couple of different methods you can use to see if there’s potential life inside an egg, or whether it’s simply a yellow yolk that won’t develop further.

Illustration of a fertile chicken egg with a developing embryo

By opening the egg

If you crack it open, a fertile egg can be identified by a small white circle on the yolk, that has a ‘bullseye’ like shape - i.e. one small white circle, with another white ring on the outside of it. This is created by a cluster of cells that, if incubated, will hopefully develop into a baby chick.

By candling

If you're looking to incubate your eggs, then the only way to tell if the egg is fertile is by incubating it for a few days, and then candling the egg to see its progress.

This involves going into a dark room, and shining a bright light underneath the large end of the egg. If the egg is fertile, then you should see a dark spot around the middle of the egg, with some spider-like veins beginning to form around it.

If its not, you should just be able to see the shape of the yellow yolk inside the egg, without any signs of an embryo or veins.

Candling must be done multiple times throughout the incubation process - on Day 4, Day 10 and Day 17. This helps identify whether the fertile egg is developing as it should, or whether the embryo may have died and needs to be removed.

Don’t lose hope!

Even if you’ve bought fertile eggs from a farm or online, they may not always progress to hatching stage, or mix ups can occur - so don’t be disheartened if not all of your embryos end up developing right off the bat. It would be unusual if they all did!

If you’re incubating, check out our range of articles on the incubation process. In addition, we sell incubators that turn the eggs, monitor humidity and temperature and does its best to ensure a high hatch rate for your fertile eggs.

Sources and further reading

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