Dark Factor Lovebird Genetics:
Dark Green, Olive, Cobalt and Mauve Explained

Walk into any Fischer's lovebird breeding room and you will find at least one bird described as "darker than normal." That darkness almost always traces back to a single mutation: Dark Factor. It is one of the most widely present mutations in the hobby — often carried without the breeder even knowing it — yet it is also one of the most consistently misunderstood. Many breeders believe Dark Factor adds extra melanin to make the bird darker. It does not. And many assume you can carry it invisibly as a split. You cannot. This guide covers exactly what Dark Factor does, the six colour forms it creates, how to predict offspring, and the common mistakes to avoid.

What Dark Factor Actually Does — The Spongy Zone

The colour of a lovebird's body feather is produced by two systems working together. The first is pigment: eumelanin (the dark melanin in the feather barbules) and psittacofulvins (the yellow-red pigments unique to parrots). The second is feather microstructure: a layer of sponge-like cells called the spongy zone (or medullary layer) that scatters short-wavelength light, producing the structural blue-green colour you see even before pigment is applied on top.

Dark Factor does not touch the pigment system. It has no effect on how much eumelanin or psittacofulvin a bird produces. Instead, Dark Factor narrows the spongy zone — it physically compresses the light-scattering layer. When the spongy zone is narrower, it scatters shorter wavelengths (shifting the structural colour toward blue and away from green-yellow), which makes the overall plumage appear denser and darker.

This distinction matters enormously for predicting combinations. Because Dark Factor works on feather structure — not pigment — it interacts with every pigment mutation (Blue, Opaline, Cinnamon, Dilute, etc.) in predictable, additive ways without altering those mutations' own effects.

SF vs DF: The Six Colour Forms

Because Dark Factor is an incompletely dominant mutation, each copy adds an incremental effect. Zero copies = normal. One copy (SF = Single Factor) = a darker bird. Two copies (DF = Double Factor, the homozygous form) = an even darker bird. This creates a three-tier progression within both the green and blue series.

Inheritance — Why No Splits Exist

This is the point where many breeders get confused, especially if they are used to working with recessive mutations like Blue or Pale Fallow where a bird can look normal while secretly carrying a gene copy.

Dark Factor does not work that way. It is dominant — meaning it always has a phenotypic effect when present. Unlike a fully dominant mutation (where one copy looks the same as two copies), Dark Factor is incompletely dominant: each copy incrementally darkens the bird. The result is that you can always tell from looking at a bird how many copies of Dark Factor it carries:

• Normal Light Green or standard Blue = zero copies. No Dark Factor at all.
• Dark Green or Cobalt = exactly one copy. SF Dark Factor.
• Olive or Mauve = exactly two copies. DF Dark Factor (homozygous).

There is no "split for Dark Factor." A bird either shows it or does not carry it. This makes Dark Factor one of the most transparent mutations in the hobby — you can read the gene dose directly from the bird's colour.

Core Pairings

Dark Factor + Blue: The Colour Ladder

Dark Factor and the Blue mutation are on completely separate gene loci and combine independently. This means a bird can carry any combination of Blue and Dark Factor doses. The result is a clean two-dimensional colour ladder with six distinct named forms — three in the green series (varying by DF dose), three in the blue series (also varying by DF dose).

The show bird combination: SF Violet Dark Blue (Cobalt-Violet)

When Violet is added to the equation, the ideal show bird combination is widely considered to be Single Factor Violet + Single Factor Dark Factor on a Blue background — commonly written as SF Violet Dark Blue or Cobalt-Violet. The Violet mutation in the presence of SF Dark Factor on Blue produces the richest, most saturated violet-blue expression. DF Dark Factor (Mauve-Violet) tends to appear too dark and muddied, while standard Blue-Violet (no DF) lacks the depth of the cobalt base. SF Violet on SF Dark Blue (Cobalt) hits the ideal balance. See the Violet lovebird genetics guide for the complete breakdown of how Violet inheritance interacts with Dark Factor across base colour combinations.

It is worth noting that the Violet mutation in Fischer's lovebirds is an autosomal incomplete dominant — exactly like Dark Factor — which means it also produces three phenotypes (no Violet, SF Violet, DF Violet) that are visually distinct. The visual assessment of a bird's Violet + Dark Factor status requires comparing body colour in standard lighting conditions. Advanced breeders often maintain written records of each bird's Dark Factor and Violet genotype rather than relying solely on visual assessment, particularly for DF birds where the phenotype can appear similar to deeply coloured SF combinations under poor lighting.

Common Mistakes and Misconceptions

Dark Factor Inheritance — How to Predict Offspring

Because Dark Factor is incompletely dominant with three observable phenotypes, predicting offspring is straightforward once you know the gene dose of each parent. Unlike autosomal recessive mutations where you need to know split status (often invisible), Dark Factor genotype is always readable from phenotype.

Normal × SF Dark (one copy)

A normal (zero copies) paired with a Single Factor Dark bird: 50% offspring will be SF Dark, 50% will be normal. No DF birds possible from this cross — DF requires two copies, which can only occur when both parents contribute a Dark Factor allele.

SF × SF — the classic three-way split

Two SF Dark birds paired together produce the classic 1:2:1 ratio of incomplete dominance: 25% normal (zero copies), 50% SF Dark (one copy), 25% DF (two copies). This is the most common Dark Factor pairing in most aviaries since SF birds are the most frequently held Dark Factor form. The 25% Light Green and 25% Olive from two Dark Green parents surprises many breeders who expect all offspring to be Dark Green.

SF × DF — skewing toward darker offspring

SF paired with DF: 50% SF offspring, 50% DF offspring. No normal birds from this cross — the DF parent contributes a Dark Factor copy to every offspring, and the SF parent contributes either one or none. The result is all birds carry at least one Dark Factor copy.

DF × DF — all offspring are DF

Two DF birds paired together: 100% DF offspring. Every offspring receives one Dark Factor allele from each parent, producing only double factor birds. This is the "lock-in" pairing for DF production — useful if your market specifically values DF Cobalt or DF Mauve birds.

Normal × DF — all offspring are SF

A normal (zero copies) paired with a DF (two copies): 100% SF offspring. The DF parent contributes a Dark Factor allele to every chick; the normal parent contributes none. Every offspring receives exactly one copy — the SF phenotype. This pairing is useful for quickly introducing Dark Factor at a controlled SF level without risking producing any DF birds.

Because Dark Factor genotype is always visible, test pairings are not required to confirm genotype. Simple visual inspection of a bird — provided you have experience distinguishing the three phenotypes — is sufficient to plan breeding outcomes. This makes Dark Factor one of the easiest mutations to work with from a genetics management standpoint.

Dark Factor on All Base Colours — The Full Colour Matrix

Dark Factor's structural mechanism — spongy zone narrowing — means it modifies the optical output of feather structure independently of any pigment. This makes it a universal colour modifier: it deepens and enriches the phenotype on every base colour combination. The effect is not limited to green and blue series birds.

Green Series with Dark Factor

The standard three-tier progression: Light Green (zero copies), Dark Green SF (one copy), Olive DF (two copies). The darkening is most visible on the body and wing coverts. The face mask colour is unchanged by Dark Factor — the orange-red face of a Fischer's lovebird remains orange-red regardless of Dark Factor dose. The back and rump feathers show the most pronounced darkening in Dark Green birds, and experienced breeders use the rump as the primary visual assessment point for distinguishing SF from Light Green at fledging.

Blue Series with Dark Factor

On a Blue base (either B1 or B2 allele), Dark Factor produces: standard Blue (zero copies), Cobalt SF (one copy), Mauve DF (two copies). The white face mask characteristic of Fischer's Blue mutations is retained unchanged at all Dark Factor doses — Dark Factor affects body structural colour only. The Cobalt phenotype (Blue SF) is generally considered the most aesthetically attractive Blue series Fischer's lovebird and commands the highest Blue-series prices in South Asian markets. See the Blue lovebird genetics guide for the full Blue mutation breakdown.

Aqua Series with Dark Factor

On an Aqua (B1/B1 homozygous) base, Dark Factor deepens the characteristic turquoise: Aqua Homo (zero copies) produces the standard saturated turquoise; Aqua Homo SF (one copy) shows a noticeably deeper teal; Aqua Homo DF (two copies) produces a slate-turquoise. The Aqua SF bird is sometimes described as an "Aqua Cobalt equivalent" in market terms — the structural deepening from Dark Factor acts on the turquoise base in the same way it acts on the blue base. See the Aqua lovebird genetics guide for the B1/B2/Homo distinction that underlies this combination.

Opaline with Dark Factor

Opaline (sex-linked recessive) redistributes psittacofulvin expression across the feather tracts. When Dark Factor is added to an Opaline bird, the structural colour deepening from spongy zone narrowing acts on both the plumage redistribution areas and the body areas simultaneously. Opaline Dark Green and Opaline Cobalt are both commercially recognised combinations — the Dark Factor deepening enhances the richness of the Opaline plumage redistribution. See the Opaline genetics guide for the sex-linked inheritance rules that determine whether Opaline can be combined with any given pairing.

Dark Factor as a universal modifier

The key principle: Dark Factor deepens the colour in every base colour combination because it operates at the structural level — independently of psittacofulvins (yellow/orange pigment) and independently of melanin (dark pigment). A Cinnamon Cobalt (Cinnamon reduces TRP1 melanin, Blue removes psittacofulvins, Dark Factor narrows spongy zone) is a structurally distinct bird from a standard Cobalt — the Cinnamon's reduced melanin combines with Dark Factor's structural deepening for a unique visual effect. The calculator on the homepage can model any combination.

The Commercial Value of Dark Factor — Why SF Dark Cobalt Commands a Premium

Dark Factor's commercial value in the South Asian and Gulf Fischer's markets varies significantly by phenotype. The relationship between dosage and market preference is counterintuitive: more Dark Factor does not necessarily mean more market value.

Why SF is often preferred over DF

SF Dark Green and SF Cobalt are aesthetically preferred by most buyers over DF Olive and DF Mauve. The DF phenotypes — Olive and Mauve — are considered too dark and muted by many market participants. Olive birds have an olive-khaki tone that many buyers find unappealing compared to the vivid dark green of an SF Dark Green bird. Mauve birds show a slate-grey-blue that can appear washed out compared to the rich depth of a Cobalt. The aesthetic "sweet spot" for most market buyers is the SF phenotype — dark enough to be clearly distinguished from wild-type, but not so dark that the vibrancy is lost.

Cobalt (Blue SF DF) — the most commercially attractive Blue series phenotype

In South Asian and UAE markets, the Cobalt Fischer's lovebird (Blue base + one copy of Dark Factor, SF) is consistently the most commercially attractive Blue series phenotype. The colour is rich, deep cobalt-blue with excellent visual appeal under any lighting. For show bird purposes, the combination of SF Violet + SF Cobalt (sometimes written as SF Violet Dark Blue) is widely considered the ideal violet expression — producing the richest, most saturated violet-blue phenotype possible in Fischer's lovebirds.

Dark Aqua (Aqua SF) — a rising premium combination

As Aqua Homo lines become more established in South Asian aviaries, the combination of Aqua Homo + Single Factor Dark is becoming a recognised premium category. The deepened teal of Aqua Homo SF is visually distinctive from standard Aqua Homo and commands a premium in markets where the Aqua SF (sometimes called Dark Aqua or Aqua Cobalt) phenotype is understood. This is still an emerging category in Bangladesh and Pakistan markets as of 2026.

2026 pricing benchmarks (BDT)

• SF Dark Green pair: 6,000–12,000 BDT. The most common Dark Factor form; widely held across all markets.
• SF Cobalt pair: 15,000–28,000 BDT. Blue series with SF Dark Factor; premium over standard Blue reflects aesthetic preference.
• DF Cobalt (Mauve) pair: 10,000–18,000 BDT. Slightly less than SF Cobalt due to aesthetic preference for SF over DF in the market.
• Dark Aqua Homo SF pair: 35,000–60,000 BDT. Aqua Homo base + one copy Dark Factor; emerging premium combination.
• Olive or Mauve birds (DF): Typically sell at slightly below SF equivalents in most markets due to the aesthetic preference for SF phenotypes.

History and Origin of Dark Factor in Fischer's Lovebirds

Dark Factor in Agapornis fischeri is an autosomal incomplete dominant mutation documented in Van den Abeele's Lovebird Compendium (2016). The incomplete dominant expression — producing three phenotypes from two alleles — makes it behaviourally similar to the Dark Factor in budgerigars (Melopsittacus undulatus), where the equivalent mutation produces Light Green, Dark Green, and Olive in the green series. The parallel extends to the blue series: budgerigars show Sky Blue, Cobalt, and Mauve in exactly the same pattern as Fischer's lovebirds with Dark Factor on a Blue base.

The Fischer's lovebird Dark Factor was documented in European avicultural collections from the mid-20th century, with the genetic mechanism understood through breeding records well before molecular confirmation became available. The spongy zone narrowing mechanism — documented by Van den Abeele as the correct physical explanation for the darkening effect — corrected the earlier misunderstanding that Dark Factor added extra eumelanin.

In South Asian markets, the Cobalt phenotype (Blue SF Dark Factor) is the most commercially traded Dark Factor variant, with established breeding lines in Bangladesh, Pakistan, and India. The Cobalt phenotype's popularity reflects both its aesthetic quality and its relative ease of production — SF Cobalt birds can be produced from any Blue × Dark Factor cross, making them more accessible than complex multi-mutation combinations. The Violet Cobalt combination (SF Violet + SF Cobalt on a Blue base) is the established show bird target in Fischer's lovebird exhibitions across South Asia and Southeast Asia.

For related content, see our Blue lovebird genetics guide, the Aqua lovebird genetics guide, and the Violet lovebird genetics guide. To model any Dark Factor combination precisely, use the Lovebird Genetics Calculator.