Introduction

This guide is designed as an easy-to-understand introduction to duck color genetics. It focuses on the genes that are well documented and commonly encountered by breeders rather than attempting to cover every known mutation.

If you'd like to study duck genetics in greater detail, two excellent references are Colour Breeding in Domestic Ducks by Mike and Christine Ashton and Storey's Guide to Raising Ducks by Dave Holderread.

Understanding Genetic Notation

Each inherited trait is controlled by a specific location on a chromosome called a locus (Plural: loci). Every locus can contain different versions of the same gene, known as alleles.

For example, the Pattern locus currently includes the alleles:

• M+ (Wild-Type Mallard)

• MR (Restricted)

• md (Dusky)

Because ducks inherit one allele from each parent, every duck has two alleles at every locus (excluding each sex-linked locus).

Example:

M+/md

Reading the Symbols

• A plus sign (+) identifies the original or "wild-type" allele.

• Alleles without a plus sign represent mutations from the wild type.

• Capital letters indicate dominant alleles.

• Lowercase letters indicate recessive alleles.

When writing a genotype, experienced breeders often leave out genes that are already understood. For example, a Welsh Harlequin may simply be written as md/md lih/lih instead of listing every unchanged gene.

Common Genetics Terms

Homozygous

A duck is homozygous when it inherits two identical alleles at a particular genetic locus—one from each parent.

Examples:

• M+/M+ - Homozygous Wild-Type Mallard

• md/md - Homozygous Dusky

• E/E - Homozygous Extended Black

A homozygous duck will always pass the same allele to its offspring.

Heterozygous

A duck is heterozygous when it inherits two different alleles at the same genetic locus.

Examples:

• M+/md - Wild-Type carrying Dusky

• E/e+ - Extended Black carrying the wild-type

• Bl/bl+ - Blue

Depending on the relationship between the two alleles (dominant, recessive, or incompletely dominant), a heterozygous duck may display the dominant trait, an intermediate appearance, or characteristics influenced by both alleles.

When a heterozygous duck carries a recessive allele that is hidden by a dominant allele, it is commonly referred to as a carrier. Although the recessive trait is not visible, it can/will still be passed to offspring.

For example, a duck with the genotype M+/md carries the Dusky allele but will usually display the Wild-Type Mallard pattern.

Pattern Locus (M)

The Pattern locus controls the basic distribution of pigment across the body.

M+ - Wild-Type Mallard

The standard mallard pattern found in wild ducks. It is dominant over Dusky but recessive to Restricted.

MR - Restricted

Restricted reduces dark pigmentation, especially across the wing coverts, creating a much lighter appearance. It plays an important role in several domestic color varieties, including Silver Appleyards.

md - Dusky

Dusky removes or weakens several classic mallard markings. Common effects include:

• Reduced or missing eye stripes

• Less iridescence in the wing speculum

• Increased pigment beneath the wings

• Reduced or absent white neck ring in drakes

Its final appearance can vary considerably because it interacts with many other genes.

Pattern Locus Genotypes:

M+/M+ = Wild-Type/Mallard

M+/md = Wild-Type carrying Dusky

MR/M+ = Restricted carrying Wild-Type

MR/MR = Homozygous Restricted

MR/md = Restricted carrying Dusky

md/md = Homozygous Dusky

Light/Dark Phase Locus (Li)

This locus determines how strongly the pattern is expressed.

Li+ - Dark Phase

The normal wild-type allele. Produces the darkest expression of the pattern and is dominant over both Light and Harlequin.

li - Light Phase

Lightens the overall pattern and is recessive to Dark Phase.

lih - Harlequin Phase

Produces an even lighter appearance than Light Phase. When paired with Light Phase, birds often show an intermediate appearance.

Light Phase Genotypes:

Li+/Li+ = Dark Phase

Li+/li = Dark Phase carrying Light

Li+/lih = Dark Phase carrying Harlequin

li/li = Light Phase

li/lih = Light Phase carrying Harlequin

lih/lih = Harlequin

Black Locus (E)

The Black locus determines whether the duck expresses its normal feather pattern or an extended black coloration.

e+ - Wild-Type (Non-Black)

This is the normal allele found in wild ducks. It allows other pattern and color genes to be visible.

E - Extended Black

Extended Black is dominant over the wild-type allele. When present, it replaces much of the normal feather pattern with black pigmentation.

Although Extended Black masks many other pattern genes, several genes still influence its appearance, including:

• Blue

• Chocolate

• White

• Pied

• Bibbed

• Other modifying genes

Some black ducks also develop rusting, penciling, or scattered lighter patches. The exact genetic cause of these variations is still being researched.

Black Locus Genotypes:

e+/e+ = Wild-type (non-black)

E/e+ = Black carrying Wild-Type

E/E = Black

Blue Locus (Bl)

The Blue locus is an incompletely dominant dilution gene. Rather than creating a completely different color, it lightens black pigment.

One copy of Blue dilutes black pigment to a slate or blue-gray shade.

Two copies dilute pigment even further, often producing a very pale blue or nearly white bird depending on the underlying genetics.

Blue affects both patterned ducks and ducks carrying Extended Black.

Blue Locus Genotypes

bl+/bl+ = No blue dilution

Bl/bl+ = Blue. Dark feathers become blue-gray.

Bl/Bl = Double Blue. Pigment is diluted much more heavily, often producing very pale birds.

Chocolate Locus (D)

The chocolate locus is a sex-linked dilution gene that changes black pigment into chocolate.

Unlike most genes, inheritance differs between males and females because the gene is located on the sex chromosome.

D+ - Wild-Type

No chocolate dilution.

d - Chocolate

Chocolate is recessive and dilutes black pigment throughout the plumage.

Because males have two sex chromosomes, they require two copies of chocolate for the trait to appear. A male with only one copy is a carrier.

Females have only one copy of this chromosome, so a single chocolate allele causes the trait to be expressed.

Male Genotypes:

D+/D+ = Wild-type

D+/d = Wild-type carrying chocolate

d/d = Chocolate

Female Genotypes:

D+ = Wild-type

d = Chocolate

White Locus (C)

The White locus controls whether pigment is produced in the feathers.

C+ - Wild-Type

Pigment develops normally, allowing all other color genes to be expressed.

c - Recessive White

When two copies are inherited, pigment production is prevented and the duck appears completely white.

White Locus Genotypes

C+/C+ = Normal pigmentation

C+/c = White Carrier

c/c = White

Runner Locus (R)

The Runner locus removes pigment from selected areas of the plumage, producing white markings.

It is an incompletely dominant gene, so one copy produces less white than two copies.

r+ - Wild-Type

No pied markings.

R - Runner

A single copy usually creates a limited amount of white, most commonly on the throat, neck, or wing feathers.

Two copies generally produce much larger white areas and are responsible for the classic Fawn & White pattern.

Pied affects both patterned ducks and ducks carrying Extended Black.

Pied/Runner Locus Genotypes:

r+/r+ = No pied markings.

R/r+ = Limited white areas.

R/R = Pied

Putting It All Together

Each duck inherits one allele from each parent at every genetic locus. The combination of these genes determines the bird's final appearance.

Some genes establish the basic feather pattern, while others modify or dilute that pattern. Additional genes can remove pigment entirely or replace portions of the plumage with white.

Example Genotypes: 

M+/M+ Li+/Li+ e+/e+ = Wild-type/Mallard

md/md lih/lih e+/e+ = Welsh Harlequin

E/E Bl/bl+ = Blue

E/E d/d = Chocolate (male)

Important Notes

Duck color genetics continues to be an active area of study. While the genes listed in this guide are widely accepted, many modifiers and interactions are still not fully understood.

Two ducks with the same major genotype may not always look identical. Minor modifier genes, selective breeding, and incomplete knowledge of some loci can all influence the final phenotype.