My quest to figure out which of my seven hens were laying eggs led me to start researching egg color. Trying to determine which of my hens were producing blue/green eggs was becoming difficult. One of my hens looks like some form of Auraucana cross, maybe and Easter-Egger or Olive-Egger. My unanswered question was “would a single hen lay eggs of different colors?” Off to the search engines I went.
He says, she says
The internet is full of contradicting information. Some say of course Easter-Eggers and chickens in that class lay multiple colored eggs. Others said, no, just one color per hen. Additional responses claimed hens can lay different shades of eggs in the same color family. Finally, I found my answer thanks to a research paper titled “An EAV-HP Insertion in 5′ Flanking Region of SLCO1B3 Causes Blue Eggshell in the Chicken.” Exactly what I was looking for—a peer reviewed paper on chicken egg color. It is a very interesting read, especially if the genetic origin of the Auraucana and blue chicken eggs piques your interest.
It’s in the genes
Hens that lay white eggs, will always lay white eggs. Hens that lay brown eggs can lay eggs in shades of browns, ranging from dark brown to almost light pink. Those that lay blue or green eggs will only lay eggs in shades of blues and greens. Even the blue/green eggs of the Auraucana are different than truly blue eggs.
All eggs start out white. Hens that lay white eggs lack the genes which produce colored eggs. A hen that lays white eggs will never start to lay colored eggs—not even very light colors.
Brown eggs are caused by the pigment protoporphyrin, which adds the color at the end of the shell development process. Break open a brown egg and remove any membrane from the inside of a shell fragment and you will notice that the inside of the shell is white. The brown coloring on the outside of the shell can be rubbed off. A hen that lays brown eggs, no matter what breed, will only lay eggs in shades of brown to pink. The shade of brown will vary due to breed, temperature, stress, age, health, and diet.
Blue and green eggs are a unique situation. The eggs are colored by the pigment oocyanin, which adds the color during the early formation of the shell. Break open a blue or green egg and look at the inside of the shell–it will be blue. Green eggs are caused by the hen being able to produce both pigments—blue and brown. Genetics dictates whether a hen will lay truly blue eggs or green/blue eggs. Blue eggers lay eggs in shades of blue. Green eggers lay in shades of green. Stress, breed, environmental factors, health, and age all play a part in how dark or light the shade is.
Will a single hen lay multiple colored eggs?
This takes us back to my original question. The answer is no—genetics dictates the color she is able to lay. There may be subtle shading within her color range. Weather, especially temperature, can impact egg color. Young hens who are just beginning to lay may have eggs that darken over time. Older hens approaching the end of their laying days will gradually have smaller eggs that lighten in color.
Did this post help you? Leave me a comment, I’d love to hear about your flock.
–Lynda, a city chick gone country.