Self Colors in Ducks: Chocolate

Self Colors in Ducks: Chocolate

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Chocolate self-colored ducks are a somewhat rare phenotype seen in domestic duck breeds. The Chocolate Runner and some Call ducks were the most commonly seen in the past; more recently, the color has been transferred to Cayuga and East Indies ducks. Extended black is the necessary base for displaying self chocolate. As such, the Dusky pattern must also be present. The brown dilution gene is what causes the actual color. Its function is to dilute the black present in the feathers to a dark brown. Since extended black causes all of the feathering to be black, all feathers will be brown when both are present. The difference in appearance between self black and chocolate is rather striking. Both are quite beautiful. They share the same green sheen and aged white factors as well. 

Brown dilution (represented by [d] genotypically, [D] stands for the absence of) is a somewhat unique phenomenon in domestic duck color genes- it is a sex-linked recessive. The sex chromosome Z carries the gene. Male ducks are homogametic, meaning their sex chromosomes are matching (ZZ). Female ducks are heterogametic with a differing pair (ZW). For this gene to be displayed, males must be homozygous with both chromosomes carrying [d], whereas females need and can only be hemizygous and carry one [d] chromosome. This presents a very interesting and useful option for producing offspring sexed at hatch by their color. Each parent gives one chromosome to their progeny. All resulting female offspring will display brown dilution if a homozygous [d] male breeds with a non-brown [D] female. All males produced will carry one chromosome, but they will not display the color.  This is known as “split” when referring to the heterozygous male. When mating a split male and a non-carrying female, 50% of female offspring will display brown dilution. If a split male breeds with a hemizygous female, the mating will produce a ratio of 50% m/f offspring that display [d], 25% split males, and 25% non-carrying females. The ability to sex birds at hatch can help cull excess males without waiting for adult feathers to grow or eliminating any possible mistakes with vent sexing. 

Indian Runner ducklings, with a self-chocolate duckling in the rear. Photo by Sydney Wells

As ducklings, self chocolate birds appear much like self black — the only difference being the primary down color. A bib may be present until the adult plumage comes in. This is not always the case, although most often, it is. The beaks, legs, and feet remain the same colors as they would in the absence of brown dilution. The adults display the same green sheen caused by prisms within the feathers refracting light as self black ducks. As the birds continue to age and molt, an increasing amount of white feathers will replace colored feathers. This occurs mainly in females. Males that age in this way are less desirable for breeding as the young progeny could risk losing color more quickly. The degree of green sheen seems to be tied to the amount of white feathering occurring in aging females — the greater one is, the other will be. For this reason, females over two years old showing a good deal of white feathering make good breeding stock. Sunlight will also cause undesirable lightening of the feathers — this is rectified at molt when new feathers grow in and are also unavoidable for the most part. 

Self chocolate ducks can be affected by two different dilution factors: Blue and Buff. The blue dilution correlates to Lavender and Lilac in the way Blue and Silver Splash do in self black ducks. Buff dilution lightens self chocolate to what has been called Milk Chocolate. The degree of dilution is comparable to heterozygous blue dilution in self-black birds. The buff dilution can also be applied along with the blue dilution to lighten both the hetero and homozygous forms further. These dilution factors will be covered more in-depth in subsequent articles. The availability of these two factors with the brown dilution creates eight different self-colored variants to the original extended black.  

Group of Chocolate Indian Runner ducks. Photo by Sydney Wells.

Generally, when people think of or see brown domestic ducks, it is the Khaki Campbell. Although the breed does display brown dilution, I feel self chocolate birds are deserving of more recognition in this field of color. The absence of visible pattern, along with the addition of a beautiful beetle green shine in the sunlight, is certainly a sight worth admiring. Chocolate Cayuga is a breed I have raised for a few years in both the standard dark and milk chocolate varieties. On a bright summer day, the aesthetic of these birds is unparalleled by other brown breeds. They have been a much-appreciated addition to the litany of waterfowl colors and types I’ve collected throughout my life. If given the opportunity, I can only imagine this phenotype would be equally revered in the collections of other backyard poultry lovers.

CRAIG BORDELEAU raises rare, threatened, and unique waterfowl in southern New England. He preserves heritage breeds, and researches domestic duck plumage genetics, as his main breeding focus

Originally published in the December 2021/January 2022 issue of Backyard Poultry and regularly vetted for accuracy.

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