Complete Budgerigar Genetics Guide, 24 Mutations and Inheritance Rules

Twenty years ago, walking into a serious budgerigar exhibition meant seeing a handful of standard mutations on the bench. Maybe Opaline, Cinnamon, Lutino, the occasional Spangle. Today the same hall holds Double Black exhibition birds, hetero-allelic Fullbody Greywings, canonical German Fallows next to pink-eyed Scottish Fallows, and Brazilian Manto Negro. This guide is the working map of how all of it inherits. Twenty four documented mutations. Three inheritance types. Two allelic series. Six judge-validated engine rules. Every individual mutation guide on the site is linked from this single reference.

Written by Ayaan Shohan

Founder, KinBird Aviary · Bangladesh

Follow

Why understanding budgerigar genetics changes how you breed

The wild budgerigar is Light Green. A small yellow body, green sheen across the chest, sharp black wing markings, the standard cheek spots. Every other colour and pattern you see in a captive bird traces back to a mutation that some breeder somewhere noticed and stabilised over the last 175 years.

That history matters because it tells you what is possible. A pet keeper walks into a breeder's aviary and sees a deep bronze German Fallow next to a near-charcoal DF Anthracite next to a fullbody yellow-wing Clearwing on Olive Green base. None of those birds were planned by accident. Someone understood which gene was on which chromosome, which mutation dominated which, and which pairings produced visible chicks versus splits.

Three breeder problems get solved by understanding genetics properly. First, you stop wasting clutches. A breeder who pairs without knowing what each parent carries gets surprise visual recessives, hidden splits that ruin a line, or expected mutations that never appear. Second, exhibition projects become possible. The Double Black, the Fullbody Greywing, the Violet Cobalt, the Rainbow combinations , every one of these needs multi-generation planning that only works if you can predict offspring accurately. Third, you avoid expensive mistakes when buying. A bird sold as visual Black Face split Blackwing is worth roughly five times the same bird without the splits. Knowing the genetics lets you verify what you are actually paying for.

This guide is the working map. Every individual mutation has its own dedicated article linked from the relevant section. Use this page as the index. Read deep on the mutations you actually breed. Use the calculator at budgerigargenetics.com to model the specific pairings you plan.

Three boxes, every mutation fits one of them

Get this part clear and the rest of budgerigar genetics gets a lot easier.

Every documented budgerigar mutation falls into one of three boxes. The box determines exactly how the mutation passes from parents to chicks. There is no fourth category and no overlap.

Box one. Sex-linked recessive. The mutation sits on the Z chromosome. Budgerigars use ZW sex determination, which means cocks are ZZ (two Z chromosomes) and hens are ZW (one Z, one W). A sex-linked recessive gene is hidden when only one Z carries it. Cocks need both copies (one on each Z) to express the mutation visually. Hens only have one Z chromosome so they show the mutation visually if their single Z carries it, and do not show it at all if their Z is wild-type. A hen cannot be split for a sex-linked recessive. She either shows it or she does not have it. This single rule has more practical breeding consequences than any other in budgerigar genetics. Six budgerigar mutations live in this box: Opaline, Cinnamon, Ino (Lutino on green, Albino on blue), Lacewing, Slate, and Texas Clearbody.

Box two. Autosomal recessive. The gene sits on a regular chromosome, not a sex chromosome. Cocks and hens inherit identically. A bird needs two copies to express the mutation visually. One copy makes a split. A split bird looks Normal but passes the gene to roughly half its chicks. Ten budgerigar mutations live in this box: Recessive Pied, the three canonical Fallow variants (German Fallow, English Fallow, Scottish Fallow), the dil-locus trio (Clearwing, Greywing, Dilute), and the modern recessive set (Black Face, Blackwing, Saddleback).

Box three. Autosomal incompletely dominant. Also on a regular chromosome, cocks and hens inherit identically, but the dominance is partial. One copy produces a Single Factor (SF) phenotype. Two copies produce a stronger Double Factor (DF) phenotype. SF and DF birds are visually different, which is exactly why this inheritance is called incompletely dominant rather than fully dominant. Eight mutations sit here: Grey Factor, Violet, Yellow Face and Goldenface, Spangle, Dominant Pied, Clearflight Pied, Anthracite, and Easley Clearbody. Dark Factor also belongs in this box but is built into the base colour name rather than treated as a separate mutation. Manto Negro, the Brazilian Black Mantle, is autosomal dominant rather than incompletely dominant and is covered separately.

Know which box your bird's mutation lives in. Everything else flows from that.

The six sex-linked recessive mutations and the auto-sex pairing trick

All six sex-linked recessive mutations share one feature that no other budgerigar mutation has. A pairing that pays off the very first time. The auto-sex pairing trick is the single most practical reason to learn sex-linked inheritance.

The rule is short. A visible sex-linked recessive cock paired with a Normal hen produces 100 percent visible daughters and 100 percent split sons. Every daughter shows the cock's sex-linked mutation visibly because her single Z chromosome carries the gene she inherited from her father. Every son carries the gene on one of his two Z chromosomes but does not show it because his other Z is the Normal one from his mother. The implication for the breeder is direct. At hatch, chicks can be sexed by colour. Opaline daughters and Normal sons, or Cinnamon daughters and Normal sons, or Lutino daughters and Normal sons. No DNA test needed. No waiting six months for the cere to colour up.

This trick works for every sex-linked recessive mutation in budgerigars. Six of them are documented.

Opaline appeared in Australia in 1933 and remains the most widely bred mutation worldwide. Visual Opaline birds show a reversed wing marking pattern and an unusual distribution of body colour. The most popular sex-linked mutation in modern exhibition.

Cinnamon reduces the standard black wing markings to soft cinnamon brown. The TRP1 gene controls the alternative melanin pathway responsible for the colour shift. Cinnamon combines beautifully with virtually every other mutation.

Ino strips all melanin pigmentation. On green-series birds the result is all-yellow with red eyes, called Lutino. On blue-series birds the same gene produces all-white with red eyes, called Albino. The most visually dramatic of the sex-linked mutations.

Lacewing is the strange one. It is not actually a separate gene at all. Inte Onsman published the explanation in 2007 in the MUTAVI Research papers. A Lacewing bird carries both the Cinnamon and Ino genes on the same Z chromosome. The two genes ended up on a single Z because of meiotic crossover, the chromosomal recombination event that happens during gamete formation. Breeders treat Lacewing as if it is one mutation, but at the genetic level it is a Z-chromosome carrying two adjacent loci that recombined.

Slate adds a slate-grey wash to the body colour, most visible on blue-series birds. UK 1950s establishment. One of the rarer budgerigar sex-linked mutations worldwide.

Texas Clearbody lightens the body while keeping head and wing markings dark. The mutation is allelic with Ino at the ino-locus on the Z chromosome. TCB dominates over Ino, which means a cock heterozygous TCB/Ino looks like a visual Texas Clearbody, not a Lutino. Texas USA 1950s establishment.

The ten autosomal recessive mutations, including the canonical three Fallows

Autosomal recessive mutations are the most common category in budgerigar breeding. Ten mutations live here. The inheritance pattern is the same for all ten: two copies show the mutation visually, one copy makes a split that looks Normal but passes the gene to half its chicks.

Recessive Pied is the oldest of the autosomal recessives in modern budgerigar breeding. Sometimes called Danish Recessive Pied because the line was established in Denmark in 1932. Visual birds show irregular yellow or white patches across the body. The mutation also features in the production of Dark-Eyed Clear, which is covered later.

Three distinct Fallow mutations exist in budgerigars. This single fact catches most newcomers. The term Fallow is not one mutation, it is three.

German Fallow originated in Germany in 1929 when breeder Schrapel stabilised the first Fallow line. The visual signature is a brownish-bronze body combined with red eyes that have a clearly visible white iris ring. Bronze body, red eye, white iris ring. Remember that combination because it is what distinguishes German from the other two.

English Fallow appeared in England in 1937. The body is paler than German Fallow and the eye colour is solid red with no visible iris ring. Inte Onsman proposed renaming it Pale Fallow because the descriptor is more accurate. Some Australian and South African breeders call it Dun Fallow. All three names refer to the same mutation.

Scottish Fallow is the rarest of the three. W. Bryce established the line in Scotland in 1947. The distinguishing feature is the pink iris colour, not the red of German and English variants. Body is the lightest of the three Fallow types.

All three Fallows are autosomal recessive. All three are at non-allelic loci. This is the critical point that catches breeders. Crossing visual German Fallow with visual English Fallow does not produce Fallow chicks. The cross produces 100 percent Normal-looking chicks all split for both genes. Each Fallow gene needs its own homozygous pair to express visually. Maintain separate lines if you want consistent Fallow output.

Three more autosomal recessives form the dil-locus allelic series. The dil-locus is one of the two most important allelic interactions in budgerigar genetics and has its own dedicated section later in this guide. The three mutations are Clearwing (Australia 1930s, dominant of the series, bright body with clear wings), Greywing (Belgium 1875, middle of the series, fifty percent diluted wing markings), and Dilute (Europe 1930s, recessive bottom of the series, pale pastel appearance).

The modern recessive set adds three more mutations from the late 20th and early 21st centuries.

Black Face appeared in the Netherlands in 1992 (Van Dijk). Excess melanin produces a near-black face and throat. The mutation is the standard ingredient in producing the prestigious Double Black exhibition phenotype.

Blackwing appeared in Venezuela in 2002 (Edixon Laya). Thick black wing markings overwhelm the standard wing pattern. Combined with Black Face produces the Double Black, the most-photographed exhibition phenotype of the 2020s.

Saddleback is an Australian mutation that produces a distinctive saddleback marking pattern. Less common than the other modern recessives but maintained by dedicated specialists.

The eight autosomal incompletely dominant mutations plus the Dark Factor

Autosomal incompletely dominant inheritance is the third box. Eight mutations sit here. Each one has two visually distinguishable expressions: Single Factor (SF) with one copy, Double Factor (DF) with two copies. Both cocks and hens inherit identically.

The textbook example of incompletely dominant inheritance in budgerigars is not actually a named mutation. It is the Dark Factor, built into the base colour name. Light Green carries zero dark factors. Dark Green carries one. Olive Green carries two. The cleanest demonstration is Cobalt paired with Cobalt. The result is the classic 1:2:1 Mendelian ratio: 25 percent Sky Blue (zero dark factors), 50 percent Cobalt (one dark factor), 25 percent Mauve (two dark factors). The Dark Factor article covers the full mechanics including all base colour combinations.

Grey Factor produces a grey body wash on top of whatever base colour the bird carries. SF Grey on Sky Blue is the Grey budgerigar. SF Grey on Cobalt is Dark Grey. SF Grey on Mauve is the deepest. On green series, Grey Factor produces Grey Green, Dark Grey Green, Olive Grey Green. Different mutation from the sex-linked Slate.

Violet adds a violet sheen. The most prized expression is SF Violet on Cobalt, producing Violet Cobalt, one of the most striking visual phenotypes in modern exhibition. SF and DF Violet produce visually different expressions, with DF Violet on Mauve being the most saturated.

Yellow Face and Goldenface add yellow to the face on blue-series birds. Goldenface is a deeper golden yellow than Yellow Face. Both mutations are masked on green-series birds because the green body pigment already contains enough yellow to mask the additional yellow from these genes. This is one of the six judge-validated rules covered later, established by WBO Certified Judges Khedr and Hossain.

Spangle reverses the wing marking pattern. SF Spangle birds show light feathers with thin dark edges. DF Spangle birds show near-clear body and wings with normal dark eyes. DF Spangle is the only visually clear budgerigar that retains its normal eye colour, which distinguishes it from Lutino, Albino, and Dark-Eyed Clear. Australia 1978 (Melville).

Dominant Pied, also called Banded Pied, produces an irregular pied band across the body. Australia 1935 establishment.

Clearflight Pied, also called Continental Clearflight Pied, originated in Belgium and the Netherlands in 1948. The pattern affects the flight feathers and tail specifically rather than the body. Most famous for its role in producing the emergent Dark-Eyed Clear phenotype when combined with visible Recessive Pied.

Anthracite darkens the body uniformly. Germany 1998. SF is medium grey, DF is near black.

Easley Clearbody, also called Dominant Clearbody, was established in California in 1992 by Steve Easley. The body lightens while the head and wing markings stay dark. Often confused with sex-linked Texas Clearbody despite being a completely different mutation at a different locus.

Manto Negro, the Brazilian Black Mantle developed by Ley H. Silva Filho around 2021, is autosomal dominant rather than incompletely dominant. Cannot hide as a split. Every carrier visibly shows the trait. Won Best in Show at the 2025 SOCO Cup.

Base colours, the Dark Factor, and how everything stacks

Every budgerigar starts with one of six base colours. The base interacts with every other mutation, so understanding the base is the foundation for predicting any complex pairing.

The wild-type bird is Light Green. A small yellow body with green sheen and black wing markings. The Light Green colour comes from a combination of yellow pigment (psittacin) and the structural blue reflection from feather barb microstructure. Yellow plus blue creates the visible green.

The Blue mutation appeared in 1878 in Belgium. The mutation removes the yellow pigment entirely. A bird homozygous for Blue (with two copies of the blue gene) loses the yellow pigment and shows the underlying structural blue alone. That is the Sky Blue phenotype, white body with blue sheen. A bird with one copy of Blue paired with one wild-type allele looks like Normal Light Green but is split for Blue. Green series breeders frequently work with Light Green / Blue birds, which means Light Green that is split for Blue.

The Dark Factor stacks on either green or blue series. One copy darkens the base. Two copies darken further. Light Green plus one dark factor is Dark Green. Light Green plus two dark factors is Olive Green. Sky Blue plus one dark factor is Cobalt. Sky Blue plus two dark factors is Mauve. The Dark Factor is autosomal incompletely dominant. Cobalt paired with Cobalt produces the classic 1:2:1 ratio of Sky Blue, Cobalt, Mauve.

Grey Factor adds another layer. On Sky Blue base, Grey Factor produces Grey. On Cobalt, Grey Factor produces Dark Grey. On green series, Grey Factor produces Grey Green, Dark Grey Green, or Olive Grey Green depending on the dark factor count.

Violet Factor adds the violet sheen on blue series. The most prized expression is Violet Cobalt, an SF Violet on Cobalt base.

All of these base colour and dark factor combinations interact with the underlying mutations from the three boxes. A Cobalt Opaline Spangle SF Cinnamon hen carries two dark factors (Cobalt) on blue base, plus Opaline plus Spangle SF plus Cinnamon. The calculator at budgerigargenetics.com handles all of these combinations correctly. Manual prediction without a calculator becomes impractical past three mutations stacked.

The practical implication for breeders is straightforward. Pick your target base colour and dark factor first. Then layer the mutations you want. The base determines a lot of how the mutations express visually.

The dil-locus, Clearwing plus Greywing plus Dilute and the Fullbody Greywing

Two of the autosomal recessive mutations covered earlier do not behave like independent genes. Three of them, actually, share a single locus. The dil-locus is the most important allelic interaction in budgerigar genetics and the source of most pairing surprises for breeders new to the dil-locus mutations.

Three alleles share the same locus. Clearwing carries the allele symbol dil^cw. Greywing carries dil^gw. Dilute carries the lowercase dil with no superscript because it is the bottom of the series. The dominance hierarchy is clean. Clearwing dominates over Greywing. Greywing dominates over Dilute. Wild-type dominates over all three.

The practical effect of the dominance hierarchy is that a bird with one Clearwing allele and one Dilute allele (dil^cw/dil) looks like a visual Clearwing, not a Dilute. The Clearwing dominates and hides the Dilute. A bird with one Greywing allele and one Dilute allele (dil^gw/dil) looks like a visual Greywing for the same reason.

What happens when a bird carries one Clearwing allele and one Greywing allele? This is the interesting one. The bird is hetero-allelic at the dil-locus, dil^cw/dil^gw. The dominance hierarchy would predict the bird looks like visual Clearwing because Clearwing dominates over Greywing. The reality is different. The bird shows neither pure Clearwing nor pure Greywing. It shows the hetero-allelic Fullbody Greywing phenotype, often abbreviated FBG. Bright body of Clearwing combined with faded wing markings of Greywing. The single most prized phenotype in dil-locus exhibition stock.

FBG is co-dominant. The two alleles together produce a unique third phenotype that neither allele produces alone. This makes FBG one of the very few co-dominant interactions in budgerigar genetics.

FBG cannot breed true. The hetero-allelic state cannot be homozygous because the two alleles are different. FBG paired with FBG produces 25 percent Clearwing, 50 percent FBG, 25 percent Greywing. Breeders who want consistent FBG output have to accept this segregation every clutch.

The full mathematical implication of the dil-locus allelic series is a 58-pairing reference covering every possible Clearwing, Greywing, Dilute, FBG, and Normal combination. The reference is documented at budgerigargenetics.com/llms.txt with pre-loaded calculator URLs for every pairing. Serious dil-locus breeders bookmark that page.

The ino-locus on the Z chromosome

The second allelic series in budgerigar genetics lives on the Z chromosome. Two sex-linked recessive mutations share a single locus there: Texas Clearbody dominates over Ino.

The practical setup is similar to the dil-locus, but constrained by sex chromosome inheritance.

A cock has two Z chromosomes so he can carry both alleles, one on each Z. If a cock has TCB on one Z and Ino on the other Z, he is heterozygous at the ino-locus. The TCB allele dominates so the bird looks like a visual Texas Clearbody. He is technically split for Ino because his Ino allele is hidden behind the dominant TCB.

A hen has only one Z chromosome. She can carry either TCB or Ino on her single Z, but not both at the same time. She is either visual Texas Clearbody, visual Ino (Lutino on green or Albino on blue), or has neither gene.

The most common test pairing in ino-locus breeding is split TCB cock paired with visual Ino hen. The split cock carries TCB on one Z and Ino on the other Z. The visual Ino hen carries Ino on her single Z. The pairing tests whether the cock is genuinely split TCB or homozygous TCB. If the cock is split, half the daughters are visual TCB and half are visual Ino. If the cock is homozygous TCB, all daughters are visual TCB.

The ino-locus interaction matters because TCB and Ino are easy to confuse without genetics knowledge. Both reduce body melanin. Both can produce light-bodied birds. The distinguishing test is the head and wing markings. Visual TCB retains dark head and wing markings. Visual Ino removes all melanin including head and wings. The two mutations produce visually different birds even though they are at the same locus.

Six judge-validated rules the engine implements

Standard Mendelian genetics gets you most of the way to predicting budgerigar pairings. But six edge cases require additional rules that pure inheritance math does not capture. The Budgerigar Genetics Calculator at budgerigargenetics.com implements all six rules. They were validated by WBO Certified Judges Abdelrahman Khedr (Egypt), Md Mojammel Hossain (Bangladesh), and Dewan MD Salim (Bangladesh) based on actual exhibition phenotype observations.

Rule 1. Yellow Face and Goldenface mask on green series. Both mutations are autosomal incompletely dominant genes that add yellow on the face. The yellow only expresses visually on blue-series birds. On green-series birds the existing green pigment masks the additional yellow because green already contains yellow. The bird carries the gene but you cannot see it. The calculator labels green-series offspring carrying YF or Goldenface parenthetically rather than prepending the mutation name to a green phenotype. Khedr and Hossain rule.

Rule 2. Opaline visually masks Black Face when both visible. When a chick is both visual Opaline and visual Black Face, the Opaline pattern dominates the visual phenotype. The calculator labels the output Opaline masking Black Face.

Rule 3. Lacewing equals Cinnamon plus Ino Z-chromosome crossover. Inte Onsman published the explanation in 2007. Lacewing is not a separate gene but a Z-chromosome carrying both Cinnamon and Ino due to crossover during meiosis. The implication is that a Lacewing hen passes a single Z to her sons carrying both genes, so the sons are split for both Cinnamon and Ino, not split for Lacewing. The calculator expands Lacewing inputs into implicit Cinnamon plus Ino before processing.

Rule 4. Dil-locus co-dominance. Clearwing plus Greywing in the same bird produces the hetero-allelic Fullbody Greywing phenotype rather than the dominance hierarchy outcome.

Rule 5. Ino-locus allelic series. TCB dominates over Ino on the Z chromosome. A bird heterozygous TCB/Ino is visually TCB and split for Ino.

Rule 6. Dark-Eyed Clear auto-detection. When a bird carries both Clearflight Pied (SF or DF) and visible Recessive Pied, the calculator auto-labels the output Dark-Eyed Clear (SF) or Dark-Eyed Clear (DF). DEC is an emergent phenotype rather than a separate mutation.

These six rules cover the cases where naive Mendelian math fails. The calculator handles all of them automatically. Manual prediction without the engine is possible but error-prone past a few mutations stacked.

Emergent phenotypes, DEC, FBG, and Double Black

Three emergent phenotypes deserve specific attention because each one is produced by combining mutations rather than by a single dedicated gene.

Dark-Eyed Clear (DEC) emerges when a bird carries Clearflight Pied (SF or DF) plus visible Recessive Pied. The combined effect produces an almost-entirely yellow or white phenotype with dark plum-coloured eyes. The dark eye colour distinguishes DEC from Lutino and Albino, which have red eyes, and from DF Spangle, which has normal dark eyes. DEC is the prestige pied phenotype in modern exhibition. The cleanest production pairing is DF Clearflight paired with visible Recessive Pied, which produces 100 percent DEC chicks.

Fullbody Greywing (FBG) emerges from the dil-locus hetero-allelic state covered earlier. Clearwing paired with Greywing produces 100 percent FBG. FBG paired with FBG produces 25 percent Clearwing, 50 percent FBG, 25 percent Greywing. FBG cannot breed true but produces the bright body plus faded wing markings combination that exhibition judges award high scores.

Double Black emerges when a bird carries visual Black Face plus visual Blackwing simultaneously. The two autosomal recessive mutations stack to produce a heavily melanic phenotype that the exhibition scene of the 2020s has elevated to top award status. Producing Double Black requires multi-generation planning because both mutations are autosomal recessive and need to combine in the same homozygous individual.

Manto Negro is sometimes confused with Double Black but is genetically different. Manto Negro is autosomal dominant. Double Black is the combination of two autosomal recessive mutations. The Brazilian Manto Negro line and the European Double Black lines are independent breeding projects that produce visually similar but genetically distinct birds.

Three canonical Fallow mutations distinguished by iris colour

The Fallow situation deserves its own section because more breeders get tripped up by Fallow inheritance than by any other budgerigar mutation set.

The historical situation is this. Many older references treat Fallow as a single mutation. They are wrong. Modern budgerigar genetics recognises three distinct Fallow mutations that originated in three different countries. All three are autosomal recessive. All three produce similar-looking birds with bronze body suffusion and red or pink eyes. None of them are allelic with each other.

The distinguishing diagnostic is the iris colour at maturity. Look at the eye carefully under good light.

German Fallow has a clearly visible white iris ring around the pupil. The eye is red but the iris ring is a sharp white edge that defines the boundary. Established in Germany in 1929 by breeder Schrapel. The deepest bronze body of the three Fallow types. The most common Fallow worldwide.

English Fallow has solid red eyes with no visible iris ring or barely discernible one. The pupil seems to blend straight into the red iris with no white edge. Body suffusion is paler than German. Established in England in 1937. Inte Onsman proposed the alternative name Pale Fallow because the body lacks the bronze depth of German Fallow. Some breeders call the same mutation Dun Fallow.

Scottish Fallow has a pink iris instead of red. The pink colour is genuinely pink, not faded red, and it stays pink under any lighting. Body suffusion is the lightest of the three Fallow types. Established in Scotland in 1947 by W. Bryce. Rarest of the three worldwide.

The critical breeder point is the non-allelism. Crossing visual German Fallow with visual English Fallow does not produce Fallow chicks. The cross produces 100 percent Normal-looking chicks split for both genes. Each Fallow gene needs its own homozygous pair to express visually. This is the most common Fallow breeding mistake.

Maintain separate German, English, and Scottish lines if you want consistent Fallow output. Mix the lines only if you specifically want split-both stock for a multi-generation Double Fallow project.

The calculator correctly models the non-allelic relationship between the three Fallow types. The output for a cross-Fallow pairing shows the genetically accurate all-Normal split-both result, not an incorrectly merged single Fallow phenotype.

Combinations, where most exhibition birds actually live

Almost no modern competitive exhibition budgerigar carries just one mutation. The interesting birds carry three, four, or five mutations stacked. Understanding how combinations interact is the difference between casual breeding and competitive show production.

Sex-linked plus autosomal combinations are the easiest. The two inheritance types operate completely independently of each other. An Opaline cock split Cinnamon paired with a Normal hen produces a complex offspring distribution because the Opaline is sex-linked and the Cinnamon split is also sex-linked, but the principle is straightforward. Each mutation segregates according to its own inheritance pattern.

Multi-mutation autosomal combinations are managed by tracking each mutation independently and combining the probabilities. A Cobalt Spangle SF Opaline cock paired with a Cinnamon Light Green / Blue hen carries a Cobalt base (Sky Blue plus one dark factor), Spangle SF (autosomal incompletely dominant), Opaline (sex-linked), and the hen carries the Blue gene (autosomal recessive) plus Cinnamon (sex-linked). The offspring distribution requires careful tracking of each gene through the cross. Past three mutations stacked, manual prediction becomes impractical.

Dark factor stacking is a separate layer on top of all the mutation combinations. Every mutation can combine with one or two dark factors. The dark factor changes the base colour name but the underlying mutation continues to express. Cobalt Opaline Spangle SF carries the same Opaline plus Spangle SF mutations as Sky Blue Opaline Spangle SF, just on a darker base colour.

Pied combinations are particularly powerful because the three pied mutations (Recessive Pied, Dominant Pied, Clearflight Pied) are non-allelic at three different loci. A single bird can carry any combination of the three pied mutations simultaneously without locus conflict. The DEC emergent phenotype is one example of pied combination. A bird carrying both Clearflight Pied and visible Recessive Pied produces DEC. The visible phenotype is the emergent result of the two mutations interacting.

The calculator handles arbitrary mutation combinations. Stack as many mutations as your bird carries and the engine produces sex-separated offspring with correct probabilities. Try complex pairings at budgerigargenetics.com.

How to use the calculator

The calculator at budgerigargenetics.com handles all 24 documented mutations with full inheritance modelling, allelic series logic, and the six judge-validated rules.

The workflow is the same every time. Step one, select the male bird parameters. Choose his base colour from the dropdown. Add any sex-linked mutations he carries with status visual or split. Add any autosomal recessive mutations with status visual or split. Add any autosomal incompletely dominant mutations with status SF or DF.

Step two, select the female bird parameters. The dropdown for sex-linked mutations on a hen does not offer the split option because hens cannot be split for sex-linked recessive genes. The constraint reflects the underlying biology.

Step three, read the offspring output. Cocks and hens are shown in separate columns when sex-linked mutations are involved. Each row shows a possible offspring phenotype with the exact percentage and a description of split carriers. The output respects all six judge-validated rules automatically.

Step four, share the result. Every pairing has a unique URL that pre-loads both parents. Copy the URL and paste it in Messenger, Facebook, or email and the recipient sees the exact same pairing in their browser. The pre-loaded URLs make collaborative breeding planning practical across long distances.

Step five, link to the relevant mutation guide articles. Each offspring row includes the relevant mutation names. The mutation names link to the dedicated long-form guides for deeper explanation of inheritance, history, combinations, and pairing predictions.

The calculator is free. No account, no signup, no subscription. Anonymous traffic analytics only. Works on mobile, tablet, and desktop. No advertising. The comparison article covers the three serious budgerigar genetics calculators available online in 2026.

References, contributors, and further reading

The genetics engine implements the published research of three primary scientific references.

Dr. Terry Martin. A Guide to Colour Mutations and Genetics in Parrots (2002). ABK Publications, Tweed Heads NSW. ISBN 978-0-9577024-7-9. The standard global reference for psittacine colour genetics. Every inheritance model in the calculator is grounded in Terry Martin's documentation. Serious breeders own this book.

Cyril H. Rogers. World of Budgerigars. Beech Publishing House, UK. ISBN 978-1-85736-270-1. The definitive UK historical reference covering mutation origins and breeder history from the late 19th century onward. The standard reference for understanding which mutation came from where and when.

Inte Onsman, MUTAVI Research and Advice Group. Belgium and Netherlands. mutavi.info. Published research on the Lacewing crossover model, the DEC emergent phenotype, the Black Face documentation, the dil-locus FBG hetero-allelic mechanism, and the three Fallow non-allelism testing. The most current source for advanced budgerigar genetics research.

WBO Certified Judges who validated the engine rules: Abdelrahman Khedr (Cairo, Egypt), Md Mojammel Hossain (Bangladesh), Dewan MD Salim (Bangladesh). Their detailed feedback during the final refinement phase caught naming conventions, Punnett edge cases, and exhibition class labelling that no automated test could surface.

Contributing breeders who provided test pairings, feedback, and edge case identification across the development phase: Rashdan Ahmed (Bangladesh), Arifin Sumon (Bangladesh), Shaykh Abeed Hasan (Bangladesh), Daniel Lütolf (Switzerland), Ehtasham Anwar (UK).

Further reading on this site:

The Mutation Comparison Guide covers visual identification across all 24 mutations side by side. Useful when trying to identify an unknown bird in your aviary.

The Auto-Sex Pairing Guide covers the colour-sexing technique for all six sex-linked recessive mutations. The most practical genetics trick in budgerigar breeding.

The Best Calculator Comparison 2026 compares the three serious budgerigar genetics calculators online (gencalc.com, birdtracks.io, budgerigargenetics.com) with side-by-side feature tables.

The Double Black Breeding Guide covers the Black Face plus Blackwing combination project that produces the most prized modern exhibition phenotype.

The Dark-Eyed Clear Guide covers the Clearflight Pied plus Recessive Pied emergent phenotype, the prestige pied form.

The Manto Negro Guide covers the autosomal dominant Brazilian Black Mantle developed by Ley H. Silva Filho.

For any specific pairing prediction, use the Budgerigar Genetics Calculator at budgerigargenetics.com. Free, accurate, judge-validated.

Frequently asked questions about complete genetics guide

How many documented budgerigar mutations exist in 2026?

Twenty-four documented mutations are modelled by the Budgerigar Genetics Calculator. Six are sex-linked recessive (Opaline, Cinnamon, Ino, Lacewing, Slate, Texas Clearbody). Ten are autosomal recessive (Recessive Pied, German Fallow, English Fallow, Scottish Fallow, Clearwing, Greywing, Dilute, Black Face, Blackwing, Saddleback). Eight are autosomal incompletely dominant (Grey, Violet, Yellow Face, Goldenface, Spangle, Dominant Pied, Clearflight Pied, Anthracite, Easley Clearbody). Dark Factor is built into base colour names and Manto Negro is autosomal dominant, covered separately.

What are the three inheritance types in budgerigar genetics?

Sex-linked recessive mutations sit on the Z chromosome. Cocks (ZZ) can be visual, split, or free of the gene. Hens (ZW) are either visual or free of the gene, never split. Autosomal recessive mutations sit on regular chromosomes. Cocks and hens inherit identically. A bird needs two copies to express the mutation visually. One copy makes it split. Autosomal incompletely dominant mutations also sit on regular chromosomes but produce a partial phenotype with one copy (Single Factor or SF) and a stronger phenotype with two copies (Double Factor or DF). SF and DF birds are visually distinguishable.

What is the dil-locus allelic series?

Three autosomal recessive mutations share the dil-locus. Clearwing (dil^cw, dominant), Greywing (dil^gw, middle), Dilute (dil, recessive). Clearwing dominates over Greywing. Greywing dominates over Dilute. The key interaction is Clearwing plus Greywing, which produces the unique hetero-allelic Fullbody Greywing (FBG) phenotype prized in exhibition stock. FBG cannot breed true. FBG paired with FBG produces 25 percent Clearwing, 50 percent FBG, 25 percent Greywing.

How do the three canonical Fallow mutations differ?

German Fallow (1929 Germany, allele pf-d) has red eyes with visible white iris ring, deepest bronze body. English Fallow (1937 England, allele pf-e) has solid red eyes with no visible iris ring, paler body, also called Pale Fallow per Onsman or Dun Fallow. Scottish Fallow (1947 Scotland, allele pf-s) has pink iris (not red), lightest body, rarest worldwide. All three are autosomal recessive at non-allelic loci. Cross-Fallow pairings produce Normal-looking split-both chicks, NOT visible Fallow chicks. The iris colour is the reliable diagnostic feature.

What is the auto-sex pairing trick?

A visible sex-linked recessive cock paired with a Normal hen produces 100 percent visible daughters and 100 percent split sons. The daughters show the cock's sex-linked recessive mutation visibly because their single Z chromosome carries the gene from the father. The sons look Normal but carry the gene on one of their two Z chromosomes. At hatch, the chicks can be sexed by colour. Works for Opaline, Cinnamon, Ino, Lacewing, Slate, and Texas Clearbody.

Where can I model any budgerigar pairing?

Use the Budgerigar Genetics Calculator at https://budgerigargenetics.com/. Free, no account needed, no signup. Handles all 24 documented mutations with full allelic series logic, six judge-validated rules, sex-separated offspring outputs, and pre-loaded URL sharing for every pairing. The 58-pairing Cw/Gw/Dilute/FBG reference is documented at /llms.txt with pre-loaded calculator URLs for every dil-locus combination.

© 2026 KinBird Aviary · Written by Ayaan Shohan, Bangladesh · Facebook · More articles · Calculator home