Blue Birchen Marans are my favorites on the farm. Instead of the classic copper coloration on the neck, birchens have the yellow/silvery manes. “Rusty Blue” is my primary flock rooster. He is a gorgeous bird, with a sweet but somewhat aloof personality.
Blue coloration comes as a result of the Blue-Black-Splash genes in chickens. Blue is actually dilute black. More information on this genetic pattern is available here (link to come).
Marans are known for their rich dark brown eggs. Blue Marans eggs can be somewhat lighter than the Black Copper Marans which typically have the darkest brown eggs of all the Marans types. I also notice that the egg coloration from my Blue hens tends to fade faster through the season than the Black Copper eggs – meaning the eggs start out very dark in spring, but have faded to lighter shades of brown by mid-summer.
To maintain dark eggs in this breed, it is important to always be selecting breeding birds that come from the darkest eggs. That means being able to track which chicks hatched from which eggs, and then select breeding birds from the best of those chicks as they mature.