Marans are coveted for their large, dark brown eggs. The Black Copper Marans, the most common color variation, are almost all black, with a touch of gold on their necks, and lightly feathered shanks and toes. They have a bright red single comb and red to orange eyes. This variety lays the darkest of the dark brown eggs. Though many strains of the English "clean-legged" Marans exist in the United States, such as the Cuckoo Marans, the American Poultry Association still adheres to the French standard of feathered-legged birds. 

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The dark coloring of a Marans’ egg is not due to the pigment of the egg shell; but rather it is the result of a coat of pigment which is spread onto the developed egg shell as it passes through the hen’s oviduct. You can actually scrub this pigment off of the egg with water, which you cannot do with other brown eggs. When the pigment is spread onto the shell, it can come out smooth (evenly colored) or spotted. The darkness of a Marans' egg waxes and wanes through a hen’s lifetime. She lays her darkest eggs when she first lays because it takes her longer pass the egg through her oviduct, and therefore more pigment is coated onto the egg. Marans hens are bred by selecting the hens that produce the most pigment over the longest period of time. This makes the breeding process very expensive, and in turn, makes Marans chickens and eggs expensive.

 

Additionally, the dark coloration of the egg is tied to the genetics of the bird. The chicks that hatch from the darkest eggs will lay the darkest eggs. However, the darker the egg, the lower the rate of hatch. Therefore, the coveted dark, chocolate egg laying hens are quite difficult to come by.

 

The high demand and low supply have created a vacuum filled by opportunists who breed any birds they can acquire to sell hatching eggs that fetch a high price. The birds used for breeding are typically not selected for conformity to the standard of perfection, and are quite often purchased as a trio, resulting in offspring that are the product of inbreeding or poor genetics, and do not reach their full lifespan without suffering from significant health problems.