Budgerigar Mutations: Inheritance and Model Limits

Inheritance patterns

Colour and pattern names do not, by themselves, establish a bird’s genotype. Budgerigar genetics includes autosomal recessive traits (such as blue series and recessive pied), sex-linked recessive traits (such as ino, opaline, and cinnamon), and dominant or incompletely dominant traits. Spangle and Dark factor are examples of incomplete dominance: single-factor (SF) and double-factor (DF) birds can look different. Calling these simply “dominant,” or treating Dark factor and Spangle factor as the same mutation, is inaccurate.

A sex-linked ino example

Birds have a ZW chromosome system in females and ZZ in males. Ino is a sex-linked recessive locus on the Z chromosome. A female can visibly express an ino copy on her single Z; she is not described as split for this locus. Ino appearance is named by base series: Lutino in the green series and Albino in the blue series. In an idealized cross of a visual ino male with a non-visual, non-carrier female, daughters can be visual ino and sons can be ino split. Actual outcomes can depend on pedigree and linkage between sex-linked loci.

What probabilities mean

A Punnett calculation gives expected inheritance ratios only when the entered parental genotypes and model assumptions are correct; it does not guarantee the outcome of one clutch. Unknown carriers, phenotype misidentification, linked loci, and mutations outside the model can change a prediction. This page is a bounded educational summary for budgerigars, not a claim to cover every species or all mutations. Record the mutation names used and the genotype evidence behind each pairing.

Sources

• Mervilde — Colour Genetics of Budgerigars (inheritance table)
• Bird sex chromosome system — PubMed-indexed review
• Budgerigar Council of South Australia — Genetics

Content review date: 5 October 2026