Autosomal Recessive Budgerigar Mutations
Eleven budgerigar mutations follow autosomal recessive inheritance. Both sexes inherit identically. A bird needs two copies to express the mutation. Includes the three canonical Fallow types (non-allelic), the dil-locus allelic series, Recessive Pied, and the Dark-Eyed Clear emergent phenotype.
Autosomal Recessive Mutations & Guides
Clearwing, Yellow-Wing White-Wing Genetics
Bright body, clear wings. Dil-locus dominant allele. Yellow-Wing on green, White-Wing on blue. Co-dominant with Greywing produces Fullbody Greywing (FBG).
Greywing, Diluted Wing Markings Guide
One of the oldest budgerigar mutations (1875). Wing markings diluted ~50%, paler body. Dil-locus middle allele. Co-dominant with Clearwing produces FBG.
Dilute, Suffused Yellow White Pastel
Pale pastel body and wings. Dil-locus recessive allele. Also called Suffused Yellow on green and Suffused White on blue. Surfaces unexpectedly from split Clearwing/Greywing pairings.
German Fallow, Bronze Body Red Eyes Guide
The original 1929 Schrapel Fallow. Brownish-bronze body with red eyes plus the signature white iris ring that distinguishes it from English and Scottish Fallow. Most common Fallow worldwide.
English Fallow (Pale Fallow) Guide
The 1937 English Fallow, also called Pale Fallow by Onsman or Dun Fallow. Solid red eyes with no visible iris ring, paler body than German Fallow. Non-allelic with the other two Fallow types.
Scottish Fallow, Pink Iris Bryce Fallow Guide
The 1947 W. Bryce Fallow with pink iris (not red) and the lightest body of all three Fallow variants. Rarest worldwide. Mostly maintained by UK breeders today.
Recessive Pied (Danish Pied) Genetics
The oldest pied mutation in budgerigar history. Danish 1932. Combined with Clearflight Pied produces the emergent Dark-Eyed Clear phenotype.
Dark-Eyed Clear (DEC) Genetics Guide
Not a mutation but an emergent phenotype. Per Inte Onsman MUTAVI 2007. Recessive Pied + Clearflight Pied = clear body with dark eyes.
Saddleback Budgerigar Mutation
Distinctive Australian autosomal recessive mutation producing a saddle-shaped wing marking. Inheritance and combination predictions.
Blackwing Budgerigar Mutation
Discovered by Edixon Laya in 2002, stabilized by Alejandro Álvarez, first bred in the UK by Don Dickson in March 2019. Thick black wing markings and exhibition combinations.
Blackface Budgerigar Mutation
Discovered by Mr. Van Dijk at a Dutch bird market in 1992. Documented by Inte Onsman of MUTAVI Research. Black mask, abdominal striping, the famous Double Black combination.
What is Autosomal Recessive Inheritance?
Autosomal recessive mutations sit on regular chromosomes (not the sex chromosomes). Both sexes inherit identically. A bird needs two copies of the mutant allele to express the mutation visually. With one copy, the bird is a split — it carries the gene invisibly but looks Normal. Mendelian inheritance applies: visual × visual = 100% visual, split × split = 25% visual + 50% split + 25% normal (1:2:1 ratio), split × normal = 50% split + 50% normal. The three canonical Fallow mutations (German, English, Scottish) are at different loci, so crossing two different Fallow types produces Normal-looking chicks split for both genes, NOT Fallow chicks.
All 11 Autosomal Recessive Budgerigar Mutations
- Recessive Pied — Denmark 1932, irregular yellow/white patches, also called Harlequin
- German Fallow — Germany 1929 (Schrapel), red eyes with white iris ring
- English Fallow — England 1937, solid red eyes, no iris ring
- Scottish Fallow — Scotland 1947, pink iris, rarest Fallow
- Clearwing — Dil-locus dominant allele, Yellow-Wing / White-Wing, Australia 1930s
- Greywing — Dil-locus middle allele, 50% diluted wing markings, Belgium 1875
- Dilute — Dil-locus recessive, Suffused Yellow / Suffused White
- Black Face — Netherlands 1992, near-black face and chest striping
- Blackwing — Venezuela 2002, thick black wing markings
- Saddleback — Australia, distinctive saddleback marking pattern
- Dark-Eyed Clear (DEC) — Emergent phenotype: Clearflight Pied + Recessive Pied = clear body, dark eyes
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References & Further Reading
Wikipedia: Dominance (genetics) · Mendelian inheritance · Inte Onsman MUTAVI Research · Complete Budgerigar Genetics Guide
Frequently Asked Questions
What is autosomal recessive inheritance?
A mutation on a regular (non-sex) chromosome that requires two copies to express. One copy makes the bird a split (carrier, invisible). Two copies make the bird visual. Both sexes inherit identically — there is no auto-sex shortcut for autosomal recessives.
Why does split x split produce 1:2:1?
Mendelian inheritance. Each parent passes one of their two alleles. 25% chance both pass the mutant allele (visual chick), 50% chance one passes mutant + one passes Normal (split chick), 25% chance both pass Normal (normal chick). Textbook 1:2:1 ratio.
Are the three Fallow types allelic?
No. German Fallow, English Fallow, and Scottish Fallow are at three different loci. Crossing two different Fallow types produces Normal-looking chicks split for BOTH genes — NOT visible Fallow chicks. This is the most common Fallow breeding mistake.
What is Fullbody Greywing (FBG)?
The hetero-allelic phenotype at the dil-locus when a bird carries one Clearwing allele and one Greywing allele. The bird shows bright body of Clearwing combined with diluted wing markings of Greywing. FBG cannot breed true.
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