Easter Eggers: Understanding Egg Color Genetics

Unusual colored eggs have become quite popular among backyard chicken keepers. There have been many a debate about the differences between pure blue-egg-laying breeds and the much more common Easter Egger chicken. Pure breeds such as the Ameraucana or Araucana have a specific Standard of Perfection (SOP) that is accepted by the American Poultry Assoc (APA) &/or American Bantam Assoc (ABA). The SOP is a very specific list of defined variations within the breed that must not only be present in the bird but also breed true (show consistently in the subsequent offspring) in order to consider the bird to be a pure breed. On the other hand, Easter Egger (EE) chickens are not a breed at all; they are actually a hybrid or crossbred offspring from a bird that carries a blue egg gene. All of this aside, the steps for creating an EE that lays green/blue eggs are not overly complicated. Below is a condensed explanation of breeding EasterEggers.
[Note: this is intended to be a quick guide & does not cover all details of genetics]

Genetic basics:

  • Every genetic trait is produced from a pair of genes, and in reproduction each offspring receives one gene from each parent to create a pair for its genetic traits.
  • If a chicken is homozygous, it carries the same two genes for a specific trait; heterozygous means it carries two different genes for a specific trait.
  • Some genes are dominant, meaning the dominant gene will mask any other genes present (recessive).
  • There are also other factors like alleles, modifiers and inhibitors that affect the genes for specific traits.
  • There are only two genetically determined egg colors: white and blue. The blue egg gene is dominant.
  • Brown eggs are produced by an allele that produces a brown coating over a white egg. Thus, green eggs come from a brown coating over a blue egg.
  • The allele for brown eggs is dominant, meaning if it is passed to offspring it will mask other genes, alleles, and modifiers.

Pure Ameraucana (and some other breeds) are homozygous for blue eggs (O/O). This means that all offspring from a pure Ameraucana will receive at least one blue egg gene, and since that is a dominant gene, the eggs produced will be blue.

Regular brown egg layers are homozygous for white eggs (o/o) and carry the brown shell-coating allele. [designated here by o/o]

Crossing chickens carrying the above genes results in the following possibilities:


O/o = a genetically blue egg because the O is dominant
But, don’t forget to add the dominant allele for the brown eggshell coating, now you have a green egg!

Now, what happens if you breed a 1st generation* (F1) EE to another brown egg layer?

*Must be a first generation (F1) EE to ensure it carries the O/o genetics!!

Crossing an F1 EE (green egg layer) with a brown egg layer results in the following possibilities:


And what happens if you breed two 1st generation* EE’s to each other?

*Again, this must be first generation EE to ensure they both carry O/o genetics!!

Crossing an F1 EE to an F1 EE results in the following possibilities:


Don’t forget to add in the dominant brown eggshell allele, and most of the eggs will result in shades of green or some will be brown. However, occasionally the brown eggshell allele will not be passed (or will be effected by an inhibitor, modifier, or other allele), and the results will be a nice blue egg or less commonly a white egg.

As you can see, past the first generation (F1) breeding, the genetic combination possibilities increase and become more difficult to determine exactly what genes are involved, especially in roosters that do not lay eggs. Additionally, using a non-pure breed (chickens of which you do not know the exact genetic make-up) can introduce recessive genes or genetic inhibitors that might not be obvious on the parent, but will affect the outcome of the offspring.

Note: White egg layer genes, while not dominant, typically act as an inhibitor to dilute any other egg color genes. We bred a 1st generation OliveEgger to a Leghorn, and the result was a pale olive colored egg layer.

Additionally, it should be noted that many EE’s are difficult to differentiate from a pure Ameraucana breed. Since the muff/beard genes are dominant, many EE’s will carry these genes. The gene for the pea comb is located very near the blue egg gene, and is often passed with the blue egg gene. However, while pea combs often indicate the presence of the blue egg gene, it is not guaranteed, and it also does not indicate homozygous or heterozygous genetics. For a reason that we have not studied, EE’s very often have green legs which is a good indicator of non-pure-breed genetics as the pure blue-egg breeds do not have green legs. It is extremely important to know the genetics of the parent birds in order to use the information provided here. If not starting with pure genetics, then the bird could carry any number of genetic factors that will change the outcomes – even pure birds can occasionally have some genetic faults that pop-up unexpectedly.

For your reference:
Unscrambling the genetics of the chicken’s ‘blue’ egg: Researchers have unscrambled the genetic mutation that gives the distinctive blue eggs laid by some breeds of chickens.

Find A Blue Chicken Egg? Congrats, Your Chicken Has A Virus: A new study found that a single gene, called callee oocyan, is responsible for the odd coloration of these blue chicken eggs.

Genetics Mini Series 1: Genetics of Egg Color

Genetics Mini Series 2: Breeding for Blue Eggs

Genetics Mini Series 3: Breeding For Other Egg Colors

ALL ABOUT EGG COLOR: Have you ever wondered what makes blue eggs blue or why a green egg layer might hatch from a blue or brown egg? Did you know that brown eggs are coated with a “paint” made from blood, and blue egg shells contain a chemical byproduct of bile? Read on to find out the science behind egg color.


Do you keep a running egg inventory?

We have multiple coops on our “mini” farm – 6 large coops and 3 smaller hutches to be exact! As part of our farm records, we began keeping a running inventory of eggs this past year. Knowing which coops are producing best can be advantageous in many ways. Good egg production indicates which layers are in best condition for performing at top levels. Most importantly, a drop in egg production can indicate many things that need to be addressed – notably illness or other problems like improper nutrition, an egg-eating problem, or even an egg-eating predator visiting your coops. When things on the farm get busy, it can be easy to not notice a drop in egg production in time to address an issue before it becomes a larger problem. Keeping an egg inventory is an easy way to prevent this. We simply created a monthly chart in MS Word, and we log how many eggs are collected from each coop every evening.

Unfortunately, collecting eggs from nine different sets of nesting boxes and remembering which came from which proved to be a daunting task. We likely had a few errors in our inventory counts. Since we are planning to focus primarily on egg production in 2018, we are hoping to establish a better method of organized egg collection. Mama Mo has searched for a basket or rigid bag with multiple compartments to be labeled for each coop, but apparently, that is not a common item for anyone. However, there may be an unusual solution to our dilemma.

Wash Boss by Bucket Boss

Mama Mo found an item called a Wash Boss – it’s an organizer that straps onto a 5-gallon bucket. The six pockets should be large enough to hold multiple eggs, and since it’s made for getting wet, cleaning should be easy. Of course, that still leaves us a few compartments short to be able to collect from all the coops, so we plan to also use another item called a Super Stacker (below) that fits inside the bucket.

Super Stacker by Bucket Boss

They are made to stack inside the bucket, but our plan is to put our custom herbal nest box mix in the bucket and put the divider on top. This way we can also refresh nest boxes as we go, if needed. Nothing beats consolidating chores!

We have all of our coops named, so it will be easy to label each compartment and know exactly which eggs came from which coops, especially when spring arrives and everyone is in full egg production mode. When we get it all put together and test it out, we’ll post about the pros and cons of our little “innovation”.