How genetics influence some areas of poultry breeding.

The plumage colour of a chicken is defined by two pigment types.

FEATHER COLOUR

The first is the black (sometimes dark brown) pigment melanin. The second is the yellow/red pigment pheomelanine. The ground colour of a chickens plumage is pheomelanine. Where this is absent, the bird is called a "silver" as its plumage appears white.

The silver gene allows the expression of some red features, such as red shoulders. Wildtype chickens have a ground colour called "gold". If there is a presence of red enhancers, this gold can be bolstered to a dark red colour. Conversely, gold can be diluted to a yellow or cream colour. This can give rise to silver, yellow or gold plumage.

Of course not all chickens are uniform in colour, many breeds show some degree of black patterning to the feathers, as can be seen with breeds such as Silkies. Furthermore, in some breeds such as the wildtype chicken, males and females can be identified by their sexually dimorphic colouration. Hens must be camouflaged to prevent themselves from being hunted while sitting on their eggs. Her pigment is much more ground (yellowy/brown) coloured compared to that of the male which shows brighter ground colouration with areas of black pigmentation, and a green sheen.

Although completely black pigmented birds are common, genetically, it is not as easy a colour to produce as other colour forms. The reason for this, is because the black colour enhancers or "melanizers" can function in different ways, and this can influence the way in which the melanin claims dominance. While it is true that they can increase the amount of melanin, rendering the bird completely black, they can equally just render an area of the ground colour black as well.