How chickens lay blue eggs

Blue eggs are not dyed on the outside like brown ones. The blue pigment, biliverdin, is added while the shell is forming, so the color runs all the way through. Crack a blue egg and the inside of the shell is blue too. That is the quickest way to tell a true blue egg from a pale green one, since green and olive eggs usually show blue inside with a brown layer on top.

The gene behind it

Blue shells come from a single gene, often called the blue egg gene or oocyan. It is dominant. A hen needs only one copy to lay blue eggs, and a bird with two copies passes it on to all of her chicks. This is why crossing a blue egg breed with a white egg breed can still produce blue layers, and crossing with a brown egg breed gives green or olive.

Breeds that lay blue eggs

• Ameraucana, an American breed developed for blue eggs, with a beard, muffs and a pea comb.
• Araucana, often rumpless and tufted. The tuft gene can be lethal in pairs, so they are harder to breed.
• Cream Legbar, a crested bird whose chicks can be sexed by down color at hatch.
• Whiting True Blue, a production-style blue layer.

Easter Eggers can lay blue too, but their eggs might also be green, olive or even tinted, depending on their mix.

Does blue fade?

Blue tends to stay steadier than brown, since it is part of the shell rather than a coating. Some hens still lay a little paler late in the season or as they age. The first egg a pullet lays is often one of the brightest.

Blue egg myths

Blue eggs are not lower in cholesterol or higher in nutrients. That claim gets passed around a lot, but shell color does not change the inside. Another myth is that any hatchery bird sold as an Ameraucana will lay blue. Many of those are Easter Eggers, which may lay green.

Common questions about blue eggs

Why is my blue egg turning green?

If the hen carries brown egg genes too, a light brown layer can sit over the blue and make it look green. Her eggs will look that way from the start.

Are blue eggs smaller?

Many blue egg breeds lay medium eggs, a little smaller than big production brown layers. It varies by line.

Can I hatch blue egg layers from blue eggs?

Yes, but the chicks only lay blue if they inherit the gene. Hatching from a blue layer crossed with a non-blue rooster can give mixed results.