A Basic Color Genetics Index
Admittedly, this is a BASIC index. I purposely did not include every allele I am aware of because I just feel like I don’t know enough about them to confidently write about them. I skipped the bib genes as I don’t have any personal experience with them and breeders seem conflicted as to how they actually work. I also didn’t include skin, leg, and bill color genes. There are a lot of minor modifiers that duck breeders are just now learning about that are not on this list. My hope is that as I learn more, I can update, revise, and add to this index to make it more complete.
Anyone interested in a deeper, more detailed read on duck color genetics might enjoy “Colour Breeding in Domestic Ducks” by Mike and Christine Ashton OR “Storey’s Guide to Raising Ducks” by Dave Holderread.
How to use Genotype Letters
Every locus has a certain number of alleles. (example: known alleles on the Pattern Locus are represented by M+, MR, or md)
These alleles are represented by one or more letters. Usually these letters are based on a color name; M+ comes from “mallard”)
Every duck has two sets of letters per locus. (example: M+/md)
Alleles that are the original “wild-type” are represented by a letter followed by a plus sign. (example: M+)
Alleles that are mutations from the wild-type do NOT have a plus sign. (example: MR)
Alleles that are dominant are represented by capital letters (example: M+)
Alleles that are recessive are represented by lower case letters. (example: md)
When genotype is written out using this system, often the unimportant or understood loci will be skipped. (when describing a welsh harlequin you may only write md/md, lih/lih. You wouldn’t be expected to add e+/e+ for not-black since of course the duck is NOT black!)
Now let’s move on to the fun part!
The Pattern Locus
M+ = wild-type mallard pattern. This allele is dominant to dusky but recessive to restricted.
MR = Restricted. This allele is dominant to both wild-type and dusky. It primarily lightens/whitens the wing coverts. Restricted plays a big role in producing the “Silver Appleyard” color though likely not AS big a role as previously believed.
md = dusky. Dusky has very interesting effects. The most obvious ones are the elimination of eyestripes, loss of iridescence in wing speculum, underwing pigment/pattern, and the lessening or elimination of white neck rings in drakes. However, dusky is affected by numerous other genes that cause these effects to vary considerably.
Possible Combinations
M+/M+ =homozygous wild-type mallard
M+/md =heterozygous wild-type mallard; this bird carries dusky but will most often appear grey/mallard (exceptions apply!)
MR/m+ =heterozygous restricted; this bird carries the wild-type mallard pattern but will appear restricted. (shockingly, little is known for certain about this combination)
MR/MR =homozygous restricted.
MR/md =heterozygous restricted; this bird carries dusky but is thought to appear restricted (again, little is known for certain about this combination)
md/md =homozygous dusky
The Light/Dark Phase Locus
Li+ =dark phase; wild-type. This allele is dominant to both light phase and harlequin phase. It will cause the pattern to have the color saturation of a wild mallard.
li =light phase. This allele is recessive to dark phase but not completely dominant to harlequin phase. It will cause a general lightening to the wild mallard pattern.
lih =harlequin phase. This allele is recessive to dark phase but not completely recessive to light phase. Harlequin lightens pattern even more than light phase.
Possible combinations
Li+/Li+ =homozygous dark phase; wild-type
Li+/li =heterozygous dark phase; this bird carried light phase but will appear dark phase.
Li+/lih =heterozygous dark phase; this bird carried harlequin phase but will appear dark phase.
li/li =homozygous light phase
li/lih =heterozygous light phase; this is an interesting combination as phenotypically it appears halfway between a light phase and a harlequin phase.
lih/lih =homozygous harlequin phase
The Black Locus
e+ = not black; wild type. This allele is recessive to black allowing other color genetics to express.
E =black. This allele is dominant to non-black. It overrides a lot of other color genetics causing black feathers over the whole body. The most common genetics to affect black are Blue and Brown as well as the Bib genes and the Runner/Pied gene. The factors that cause “pencilling,” “rust,” and “calico patches” are not yet fully understood though some breeders believe it may have something to do with whether the black is homozygous or heterozygous.
Possible Combinations
e+/e+ = homozygous non-black; non-black color genetics can express.
E/e+ =heterozygous black; this bird will appear black, (possibly more likely to express traits such as pencilling, rust, and calico patches, though this idea needs more research)
E/E =homozygous black
The Blue Locus (a dilution gene)
bl+ =not blue; wild type. This allele is recessive to blue. Feathers will be undiluted by blue.
Bl =blue. This allele is incompletely dominant to non-blue meaning that the effects are noticeable in the heterozygous stage but are increased in the homozygous stage. All feathers are diluted by blue; blue affects patterned feathers as well as extended black feathers.
Possible Combinations
bl+/bl+ =not blue. All feathers remain undiluted by blue.
Bl/bl+ =heterozygous blue; as blue is incompletely dominant, one dose of blue causes all dark/black areas of any patterned feather to be a shade of dark grey. In black birds one dose of blue causes a blue-grey on all feathers. There is often some black leakage.
Bl/Bl =homozygous blue; as blue is incompletely dominant, two doses of blue cause a greater effect than one dose and will lighten the feathers even more ranging from a light pigeon blue to almost white. Black birds with homozygous blue are often nearly white with black bills.
The Brown Locus (a sex-linked dilution gene)
D+ =not brown; wild type. This allele is dominant to brown. Feathers will be undiluted by brown.
d =brown. This allele is recessive to non-brown. All feathers are diluted by brown; brown affects patterned feathers as well as extended black feathers. Because brown is sex-linked, males can have two “doses” of brown, while females can only ever have one. Males need two doses of brown for the brown to express because it is recessive; therefore males can invisibly carry a single dose. Females are either completely brown or completely not brown.
Possible Combinations
D+/D+ (male) =not brown. All feathers remain undiluted by brown.
d/D+ (male) =heterozygous brown. All feathers remain undiluted by brown.
d/d (male) =homozygous brown. All feathers are diluted by brown.
-/D+ (female) =not brown. All feathers remain undiluted by brown.
-/d (female) =brown. All feathers are diluted by brown.
The White Locus (a color canceler)
C+ =not white; wild type. This allele is dominant to white. Feathers will be pigmented according to the dictates of other color genetics.
c =white. This allele is recessive to non-white. All feathers lack pigment causing the white color.
Possible Combinations
C+/C+ =not white. All feathers express other color genetics.
C+/c =heterozygous white. All feathers express other color genetics.
c/c =white.
The Pied Locus (a partial color canceler)
r+ =not pied; wild type. This allele is recessive to pied. Feathers will be pigmented according to the dictates of other color genetics.
R =pied. This allele is incompletely dominant to non-pied meaning that the effects are noticeable in the heterozygous stage but are increased in the homozygous stage. In the heterozygous stage birds may express some white primary feathers and a smidge of white on the throat/neck. In the homozygous stage birds will express white in the pattern most recognizable in the Fawn & White color variety. Pied affects patterned feathers as well as extended black feathers.
Possible Combinations
r+/r+ =not pied. All feathers express other color genetics.
R/r+ =heterozygous pied. Most feathers express other color genetics except for some white primaries and a bit of white on throat/neck.
R/R =pied.