Genetics of Mottled Chickens
Mottling is a simple recessive which means a bird needs two copies of the gene to express it or show the gene and it can carry a single copy, or be a “carrier” and not show it. Other simple recessives include single comb and yellow skin. Some carriers of certain simple recessive genes can give little clues that they are carriers and look slightly different to non-carriers but you have to look quite hard and know what you are looking for.
The Mottle
Mottling is a white tip to feathers. Usually the area behind the white is intensely black and on a black bird this shows up as not having green sheen. As birds age mottling usually develops bigger white spots and on more feathers.
Statistical Expectations of Breeding Mottled Chickens
The genetics and statistics applies to all mottled poultry; including all colours of mottled (blue, black, chocolate, lavender, red, buff), millefleur, spangled OEG, porcelain, speckled or tolbunt.
| Mating | Mottled Offspring | Non-Mottled Offspring, carriers | Non-Mottled Offspring, Non-carriers |
| Mottled to mottled | 100% | 0% | 0% |
| Mottled to carrier | 50% | 50% | 0% |
| Mottled to non-carrier | 0% | 100% | 0% |
| Carrier to carrier | 25% | 50% | 25% |
| Carrier to non- carrier | 0% | 50% | 50% |
| Non-carrier to non-carrier | 0% | 0% | 100% |
Mottled Carriers
Carriers usually show no mottling but can have the odd mottled feather on the body or haze of small mottles around the head.
Varieties of Mottled
Any colour or pattern of chicken can be mottled; all they need is two doses of the mottled gene, i.e. homozygotes. Even white which will hardly show the mottle can be mottled and breed accordingly. Tolbunts are laced or sometimes other patterns plus mottles.
Mottled Carriers
Usually mottled is considered a completely recessive gene which means it doesn’t show at all when heterozygous and the bird simply “carries” the mottled gene. Sometimes a bird that is a carrier, sometimes referred to as split for mottling will have some white tips to feathers, white frosting around the head or even largely white feathers especially on the wings.
