Autosomal Incompletely Dominant Budgerigar Mutations
Nine budgerigar mutations follow autosomal incompletely dominant inheritance. Both sexes inherit identically. Single Factor (SF, one copy) shows partial expression. Double Factor (DF, two copies) shows stronger expression. SF and DF birds are visually distinguishable.
Autosomal Incomp. Dominant Mutations & Guides
Clearflight Pied, Continental Pied Guide
Clear flight feathers and tail. SF and DF expression. Combined with Recessive Pied produces the emergent Dark-Eyed Clear (DEC) phenotype prized in exhibition.
Easley Clearbody, Dominant Clearbody Guide
Steve Easley California 1992. Body lightens, head and wings stay dark. Distinct from sex-linked Texas Clearbody. SF and DF expression. Non-allelic with TCB.
Anthracite Budgerigar Mutation
German autosomal incompletely dominant mutation. SF Anthracite = medium grey body. DF Anthracite = nearly black. Distinct from Manto Negro by uniform distribution.
Yellow Face & Goldenface Mutation
Type 1, Type 2, and Goldenface variants at the bl^pf locus. Autosomal incompletely dominant. Judge-validated rule: only visually expressed on blue-series birds. On green series the gene is carried but masked.
Violet Factor & Violet Cobalt Mutation
The most prized blue-series modifier. SF Violet Cobalt is the celebrated "Visual Violet" exhibition class. Counter-intuitively, DF often looks darker than SF. Complete inheritance + pairing predictions.
Grey Factor Budgerigar Mutation
One of the most popular exhibition mutations worldwide. Sky Blue + Grey = Grey, Cobalt + Grey = Dark Grey, Light Green + Grey = Grey Green. Textbook 1:2:1 ratio in SF × SF pairings.
Manto Negro (Brazilian Black Mantle)
The newest melanistic budgerigar mutation. Developed by Ley H. Silva Filho in Brazil, the variety that won Best in Show at the 2025 SOCO Cup. Complete breeding guide with Punnett squares.
Dominant Pied (Banded & Clearflight)
Two separate pied genes, the Dark Eyed Clear emergence, and how to plan pairings for show class pied lines. Banded Pied and Clearflight Pied differences explained.
Spangle (SF & DF)
Reverse wing markings, the Mendelian 1:2:1 ratio, and why DF Spangle birds are often confused with Lutino or Albino. Single Factor vs Double Factor breakdown.
Dark Factor (Sky, Cobalt, Mauve)
The cleanest Mendelian 1:2:1 example in budgerigar genetics. Light Green to Olive, Sky Blue to Mauve, by simple gene dosage. SF and DF explained.
What is Autosomal Incomp. Dominant Inheritance?
Autosomal incompletely dominant mutations sit on regular chromosomes. Both sexes inherit identically. Unlike autosomal recessive, one copy of the mutant allele is enough to show a visible effect — this is called Single Factor (SF). Two copies produce a stronger effect called Double Factor (DF). SF and DF birds are visually distinguishable. The textbook example is the Dark Factor: Cobalt × Cobalt produces 25% Sky Blue + 50% Cobalt + 25% Mauve, the classic 1:2:1 Mendelian ratio applied to incomplete dominance. Manto Negro is the only fully dominant budgerigar mutation — it has no SF/DF distinction and cannot hide as a split.
All 10 Autosomal Incompletely Dominant Budgerigar Mutations
- Dark Factor — Built into base colours: Sky/Cobalt/Mauve, Light/Dark/Olive Green
- Grey Factor — Grey wash overlay, SF/DF distinguishable
- Violet — Violet sheen, iconic on Cobalt base
- Yellow Face / Goldenface — Yellow face on blue-series, masked on green
- Spangle — Reverse wing markings (SF), near-clear body with dark eyes (DF)
- Dominant Pied (Banded) — Australian Banded Pied, SF/DF expressions
- Clearflight Pied — Clear flights and tail, produces DEC with Rec Pied
- Anthracite — Germany 1998, medium grey (SF) to near-black (DF) body
- Easley Clearbody — California 1992, body lightening with dark head/wings
- Manto Negro (fully dominant) — Brazil 2021, dark mantle pattern, no splits possible
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References & Further Reading
Wikipedia: Incomplete dominance · Dominance (genetics) · Inte Onsman MUTAVI Research · Complete Budgerigar Genetics Guide
Frequently Asked Questions
What is autosomal incompletely dominant inheritance?
A mutation where one copy of the mutant allele produces a partial visible effect (Single Factor / SF) and two copies produce a stronger effect (Double Factor / DF). Unlike recessive mutations, the gene shows even with one copy — but the SF and DF expressions are visually different.
SF vs DF — what is the difference?
SF = Single Factor = one copy of the mutant gene = moderate expression. DF = Double Factor = two copies of the mutant gene = stronger expression. Examples: SF Violet shows violet sheen, DF Violet shows deeper violet. SF Spangle reverses wing markings, DF Spangle clears the body almost entirely (but with normal dark eyes).
Why does Cobalt x Cobalt produce 1:2:1?
Cobalt = Sky Blue + 1 Dark Factor (SF). Cobalt x Cobalt = both parents pass either a Dark Factor or no Dark Factor with 50/50 probability. Result: 25% no Dark Factor (Sky Blue), 50% one Dark Factor (Cobalt), 25% two Dark Factors (Mauve). Textbook 1:2:1.
Is Manto Negro incompletely dominant?
No. Manto Negro is fully dominant. There is no SF/DF distinction. Any bird with one or two copies looks identical. No splits possible — every Manto Negro bird visibly shows the mutation. It is the only fully dominant budgerigar mutation we know of.
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