The wildtype base (e+)
The Extension gene decides how black (eumelanin) is distributed over the body. Its wildtype allele, e+, does the least — it leaves the ancestral partridge/duckwing arrangement in place rather than spreading black (as E does) or restricting it. A plain gold duckwing is therefore about as close to "no added colour genes" as a chicken gets: e+/e+ · s+/s+, with every other locus at its default.1
| Ground colour | Genotype | Look |
|---|---|---|
| Gold duckwing | e+/e+ · s+/s+ | Gold/red hackle and shoulders on the cock; warm gold-brown stippled hen. The jungle-fowl colour. |
| Silver duckwing | e+/e+ · S/S | The same pattern with the gold swapped for silver-white by the sex-linked Silver gene; a grey-and-white hen. |
e+ and gold (s+) are the defaults, a gold duckwing carries no non-wildtype alleles to list — so in the Compare tool its genotype line can look almost blank. That is correct, not missing data: the tool shows only the alleles that differ from wildtype, and a plain duckwing has none. Add mottling and you see just mo/mo; add blue and you see just Bl; the duckwing base underneath is always implied.
Why the cock and hen look so different
The most striking thing about the e+ base is its sexual dichromatism — cock and hen are coloured quite differently, far more than on most other bases. The cock is "black-breasted red": a glossy black breast and tail with bright red-gold hackle, saddle and wing-bow. The hen is a soft partridge brown — a salmon breast, a finely gold-stippled body, and shaft-striped hackle feathers. Same genotype, two very different birds. It is why the old British name for this colour is literally black-breasted red (describing the cock) even though the hen shows no such thing.
One genotype, several names
This single base colour collected different names in different traditions, which causes a lot of confusion:
| Name | Tradition | Refers to |
|---|---|---|
| Duckwing | British / German | The wing-bow "speculum" bar; the usual English name. |
| Partridge | Dutch / Belgian (and DB1) | The same wildtype base — "gold-partridge". |
| Black-breasted red | British (game fowl) | The same colour, named for the cock. |
One caution: in some breeds "Partridge" (as in the Partridge Wyandotte or Cochin) means the base plus the Pattern gene (Pg), which adds concentric pencilling to the hen. That is a patterned duckwing, not a different base — see the pattern genes page for how Pg organises the black into rings.
What gets built on it
Because e+ is the quiet base, most "duckwing-family" varieties are just the base plus one added gene — which is exactly why this page is worth keeping in mind:
- Blue duckwing — add one copy of Blue (
Bl); the black goes blue-grey, the gold stays. - Isabel — add recessive lavender; gold softens to straw and black to grey. See the Isabel page.
- Crele — add sex-linked barring; the duckwing pattern is crossed by pale bars (Cream Legbar, Crele Old English).
- Gold duckwing mottled — add recessive mottling (
mo/mo); white tips over the duckwing base.
You can pair any two of these varieties in the Compare tool to see exactly which single gene separates them, or plan a cross in Breeding Outcomes.
- The Extension locus is MC1R;
e+is its wildtype allele, giving the ancestral Red Jungle Fowl (duckwing/partridge) distribution of black. Kerje S et al. (2003) Melanocortin 1-receptor (MC1R) mutations are associated with plumage colour in chicken. Animal Genetics 34(4):241–248. Allele-series framework: Smyth JR Jr (1990), in Crawford RD (ed.) Poultry Breeding and Genetics — see the Genetics Guide references. Genotypes shown match the Compare tool's standard data.