Somebody commented this question on a photo I recently posted to my facebook page and it got me thinking… while I may know why chickens lay different colors, there once was a time when I had no clue why. I just accepted it for what it was. But the science nerd in me wanted to know exactly why and how they do this and I was very happy to have this question asked to me so I could explain. Any chance I get to talk about chickens makes my heart happy. So, if you want to learn why chickens lay different colors then read ahead. If you don’t care but want to look at pretty egg pictures, that’s okay too.
And I’d like to preface this by saying, I am not a chicken expert nor a scientist. I don’t pretend to be these things but I do love to learn and I love to share my knowledge and experiences with others. Here we go!
Let’s start with the basics. Every chicken egg starts as white.
The egg color is determined by the genetics of the hens, meaning different breeds have certain colors specific to them. The colors are created when pigments are applied to the eggshell during it’s formation, as well as the bloom which lends to the appearance also. We will learn about that a little later.
Blue pigment = oocyanin
Brown pigment = protoporphyrin
I don’t expect you to remember or ever pronounce these words but for the sake of being thorough I thought I’d include them. These are the name of the two pigments that get deposited on the shells as the eggs travel through the oviduct. This entire process takes about 26 hours!
The basic egg color is white and every egg will start out as such.
Breeds that lay white eggs are: Leghorns (white and brown), California Whites, Anconas, Hamburgs, & Andalusians. There are more but these are the most common.
Let’s talk about blue eggs. The blue pigment -oocyanin- actually permeates the egg shell early on in development, which tints the interior and exterior of the shell. If you ever get to crack a blue egg, take a look at the inside of the shell and notice the blue color.
Breeds that lay a true blue color are: Ameraucanas (most common), Crested Cream Legbars, and Araucanas (rare). The blues will range from a pale blue to a striking sky blue.
When a chicken lays a brown egg, the base is white and the brown pigment -protoporphyrin- is deposited late in the process of forming the shell and this pigment (unlike the blue) does NOT penetrate the interior of the egg. It only tints the surface. When you crack a brown egg, look at the inside – it will still be white! The brown shell color is influenced by more than a dozen different genes giving brown eggs a wide variety of tones and shades. They range from a deep chocolate color to a barley tinted off-white.
Breeds that lay brown eggs: There are many breeds but to name a handful of common ones, you have the dark brown layers like French Black Copper Marans (and other Maran varieties), Barnevelders, & Welsummers. Medium browns include sex-link breeds (like the popular ISA Brown and Golden Comet), Rhode Island Reds, & Delawares. Light brown to tan laying chickens include Australorps, Orpingtons, Dominiques, and Sussex varieties. Sometimes they even can be cream/pink.
Now let’s have some fun!
Now things can get interesting. Green eggs are produced when you cross two purebred (or not necessarily) chickens together, one of a brown egg and one of a blue egg. Think about it. If you take a brown egg laying hen and breed her with a blue egg rooster, a resulting hen from that match will likely lay an egg of a greenish hue. Why? Because she would receive a gene from each parent and will have blue applied to the shell early in development, and towards the end of the egg’s making that brown pigment is applied to the outside, thus tinting it green. Pretty neat!
Breeds that lay green eggs: The most common green egg layers are not actually a purebred, but a crossbreed! Easter Eggers and Favaucanas. One purebred that lays a green egg is the Swedish Isbar, imported into the US just this century.
The “Easter Egger” is a very popular bird. They are usually crossed with an Ameraucana. They lay a variety of colors from sage green, seafoam green, dark green, light blue turquoise, and even pink. It all depends on what they’re crossed with. They often will have muffs and/or beards which are adorable on their little faces! They tend to have green or grey feet and legs and pea-shaped combs all of which are characteristics of the Ameraucana. They are intelligent, good at avoiding predators, get along with other chickens, and are friendly with people. An over all great bird to have i your flock! So great that we have 7 ourselves (6 hens and 1 rooster). Check out the album at the end of this blog post to meet our EEs.
Taking it one step further, we can breed for what we call olive eggs. These eggs tend to be a darker green in color (a true olive) and can range to a brownish-green as pictured here. These beautiful eggs are from a breeder in Texas called Sky Girl Farm. I became enchanted by her gorgeous earthy tones her eggs have and last month I purchased a half dozen of hatching eggs from her of varying generations of olive eggers. (They’re due to hatch within 24-36 hours actually)!
Breed that lays an olive eggs is: the Olive Egger! It is another hybrid chicken breed, and is a cross between a dark brown egg chicken and a blue egg chicken. The proper breeding for an OE would be a blue egg laying HEN covered by a dark brown egg ROOSTER. If it’s the other way around (brown egg hen covered by blue egg rooster) this would be an Easter Egger. Common roosters used are of the Marans and Welsummers, and common hens used are Ameraucanas and Crested Cream Legbars each combo resulting in a different shade of olive.
Furthermore, there are many generations of OEs. An F1 OE is the very first cross. Often times, a hen produced of this mating will be bred back to the same or another brown egg rooster so the resulting offspring lay an even darker olive. These are called F2, F3 and so on. The eggs pictured above are F1, F2, F3 and F4. If we get a good hatch and I’m lucky enough to get some hens I should have some nice and dark eggs produced!
Are you still with me? That’s a lot of science and info packed into one blog post but there’s one more thing to touch on, and that’s the bloom. The bloom is the natural coating on the eggshell that seals the pores. It is applied right as the hen is laying her egg as it comes out. It’s purpose is to prevent bacteria from getting inside the shell, and reduces moisture loss from the egg. This is why farm fresh eggs can be stored at room temperature, so long as they haven’t been washed. Bloom thickness varies from hen to hen, and when applied thickly it gives a pastel matte effect on top of the color. A heavy bloom can cause tan or brown eggs to look pink, chocolate eggs to look plum or purple, and olive eggs to look grey or lilac.
So how was that for a crash course in egg colors? I hope I wrote it well enough so it’s easily-followed. It fascinates me and I love to share and educate about chickens. Here’s some more photos of our beautiful eggs! Don’t forget to check out the end of the post for a gallery of our chickens and what eggs they each lay!