Peach-faced Lovebird colour genetics

    The science of Peach-faced Lovebird colour genetics deals with the heredity of colour variation in the feathers of the species known as Agapornis roseicollis, commonly known as the 'Peach-faced Lovebird' or 'Rosy-faced Lovebird'.

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Peach-faced Lovebirds have the deepest range of mutations available of all the Agapornis species. Generally speaking, these mutations fall into the genetic categories of Dominant, Co-dominant, Recessive, and Sex-Linked Recessive (referred to simply as "sex-linked"). While this seems fairly straight-forward, it can quickly become confusing when a single specimen has multiple examples of these mutational traits.

A good place to start in a quest for an understanding of Peachfaced mutations would be with a Peachfaced Lovebird’s base color. All Peachfaced Lovebirds, without exception, will belong to one of these two base colors; specifically, Green-series (also referred to as Wild Green), which is a Dominant trait, and Blue-series, which is a Recessive trait. Within the Blue-series base color, there are currently two recognized variants – Dutch Blue (also known as Aqua) and Whitefaced Blue (also known as Turquoise). Additionally, these recessive Blue-series traits of Aqua and Turquoise are alleles, and when an Aqua allele and a Turquoise allele are matched up in a Peachfaced Lovebird, the resulting variant is referred to as a “Seagreen” (also known as “AquaTurquoise”). As the Blue-series alleles are Recessive, a bird must receive one of the blue-series alleles from each parent in order for the blue-series trait to be seen visually. A bird that has only one recessive gene for a specific trait is said to be “split” for that trait. Thus, a bird who receives a green base-color gene from one parent and a blue-series gene (say, Aqua) from the other parent would be visually Wild Green (as Green is Dominant), but “split” for Aqua.

Beyond the base coloring of a Peachfaced Lovebird, there are mutations that exist independently of any other mutation. Again, to simplify things for the purposes of this article and in order to keep the discussion manageable and understandable for a lay-person, these mutations are of three distinct types: Co-dominant (exemplified by the Orangefaced, Dark and Violet mutations), Recessive (exemplified by the Edged Dilute mutation), and Sex-Linked (exemplified by Lutino, Pallid [also known as Australian Cinnamon], American Cinnamon, and Opaline mutations).

With Co-dominant traits, only one parent bird needs to provide the genetic information that makes up a chromosome pairing in order for the trait to be seen visually (referred to as a Single Factor for that trait) - although a passing of the genetic information from both parents will create a stronger and more easily seen example of the mutation (referred to as a Double Factor for Dark or Violet, and simply called “Orangefaced” for a Double Factor Orangefaced bird). However, with the recessive traits, the particular mutation can be seen visually only if each parent passes a recessive gene for the particular trait. Thus, while one can visually distinguish a bird with only one Co-dominant gene, such as a Single Factor Orangefaced Peachfaced, a bird with only a single recessive gene (as in the aforementioned Edged Dilute) will NOT been seen visually; it MUST be paired with an example from each parent in order for the trait to show visually. As with the base-color recessive traits, a bird that has only one recessive gene from one parent’s contributed genetic code is said to be “split” for that trait (example – split for Edged Dilute).

This brings us to Sex-Linked traits. These traits are a little bit more complex, due to the fact that these recessive traits are carried on the genetic information which also determines the gender of a bird. These genes are usually referred to in simplified terms as “X” and “Y” genes. In mammals, it is the male that determines to the sex of their offspring, in that mammal males have one “X” gene and one “Y” gene on a chromosome pairing (XY) and can pass either to an offspring - while a mammal female can only pass an “X”, due to their chromosomal pairing of “XX”. However, in birds and reptiles, this pairing is just the opposite: thus, in Lovebirds, it is the FEMALE which has an “XY” pairing and thus determines the sex of an offspring, depending on whether the mother passes an “X” gene or a “Y” gene.

It is on the “X” gene that the genetic information for sex-linked recessive traits is passed. Being that a sex-linked trait is a recessive trait, each “X” in a chromosomal pairing must have the recessive trait encoded within it, or the trait will not show visually. However, a female bird only has one X gene, and that gene is paired not with another X, but rather with a Y. Because of this, if a female bird inherits an X from her father that has the sex-linked information attached to it, the female will be visual for the sex-linked recessive trait, because there is no second X to match up with the X passed from the father. This is only true of female birds; since male birds, by genetic definition, must have two X genes (XX), both X genes must have the same sex-linked recessive information in order to show that sex-linked recessive trait visually.

With this information, one can deduce that there are an incredible number of different mutations that a single Peachfaced Lovebird could possess – so many so that one could not possibly hope to provide a photographic example of every possible mutational combination while at the same time keeping the collective work “brief” by any definition of the word. When one considers that multiple mutation combinations are easily possible (examples: “Orangefaced Single Dark, Double Violet Opaline Peachfaced Lovebird” or “Aqua Double Dark American Cinnamon Pied Peachfaced Lovebird”), one can see that a list comprising of every possible mutational combination would be VERY long indeed.

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