Cockatiel colour genetics

Cockatiel specimen combining the opaline (c.k.a. pearled) and ADMpied (c.k.a. recessivepied c.k.a. harlequin) mutations

The science of cockatiel colour genetics deals with the heredity of colour variation in the feathers of cockatiels, (Nymphicus hollandicus). About fifteen primary colour mutations have been established in the species which enable the production of many different combinations.

Note:

Mutations

Multiple names for mutations have arisen due to the use of different names in different locations for a single colour variation. This does not mean that it is a different mutation; it only means it is a different name.

Colour mutations are a natural but very rare phenomenon that occur in either captivity or the wild.

The "normal grey" or "wildtype" of a cockatiel's plumage is primarily grey with prominent white flashes on the outer edges of each wing. The face of the male is yellow or white, while the face of the female is primarily grey or light grey, and both genders feature a round orange area on both ear areas, often referred to as "cheek patches". This orange colouration is generally vibrant in adult males, and often quite muted in females. Visual sexing is often possible with this variant of bird.[1]

"Whiteface" cockatiels have their lutein (yellow and orange) pigments deactivated by the blue gene, resulting in cockatiels with absolutely no lutein pigments whatsoever. Consequently, White-faced cockatiels are mainly grey with more or less white throughout their plumage. Whitefaced cocks display brilliant white faces while hens display basically grey faces with some white streaks. With the availability of the Whiteface mutation, the cockatiel's wide colour varieties are divided into 2 main classes (or series) ;

- Yellow base : with lutein (yellow and orange) pigments.

- White base : without lutein pigments

The "lutino" sex-linked recessive mutation is a perfect example of a type of cockatiel that are the hardest to sex visually. Lutinos lack eumelanin pigment (enabling black, brown, grey colours and tones) and are consequently yellow to yellowish-white with orange cheek-patches. Adult female lutinos as well as immature lutinos of both genders display yellow bars, dots and/or stripes on the underside of their tail feathers. Mature males however can be sex visually by their always displaying solid white coloured undersides of tail feathers.

Unfortunately, a good number of cockatiels of all ino mutations and varieties (albino (albino is not correct terminology and is known as Whitefaced Ino), Palefaced Ino (Creamino), Lutino, Opaline-Ino (Pearl-Ino)... are usually affected with a transmittable genetic flaw monstrously enlarging the bald-spot below the crest, due to irresponsible excessive in-breeding and a general lack of effort, ethics and responsibility breeders to breed it out.

A pet lutino cockatiel. Note the lack of dark pigment, including in the beak, eyes, feathering, feet, skin and toenails.

"Pied cockatiel" plumage patterns vary significantly between an individual to another, giving rise to cockatiel breeders and hobbyists' "Heavy Pied" and "Light Pied" loose distinctions. Unfortunately, the degree in piedness remains quite genetically unpredictable. However, breeding heavily pied specimens together generally produces a higher percentage of heavily pied offspring than breeding lesser pied specimens together. Ultimately, the "Pied" mutation causes the bird to lack a majority of the typical grey plumage on the breast, belly, and head. Thus "Pied" cockatiels are characterised by the degree of their yellow or yellow-white colouring in these areas. Last but not least, there are the exceptional Clearpied individuals that are solid yellowish-white or solid white just like lutino and/or albino but with normal blackish eyes and out of ADMpied (recessive pied) parentage.

It is important to know that, throughout parrot species the ADMpied (anti-di-morphic pied) gene negates the male's ability to display his species' dimorphic features. Leading to ADMpied cockatiels being notoriously difficult to sex visually but being excellent examples for studies in genetic traits. However, in monomorphic species (i.e. conures, lovebirds, macaws, rosellas, etc.) the anti-di-morphic (hence ADMpied) feature cannot be expressed but piedness still is and in these species such pied specimens are called either Recessivepied (and/or Harlequin in budgerigar).

Cinnamon and Opaline ("Pearled") mutations are sex-linked recessive. In Cinnamons, the eumelanin pigment are partially oxidized (eumelanin granules are stopped at the brown stage of their development to end up in their natural black colour state) Here is an excellent description of the pearled cockatiel:

The Pearl Cockatiels gene does not have any visual affect [sic] on the colour pigments in the bird but instead it affects the distribution of the colours that are already present. It actually decreases the spread of the grey family of pigments (melanin) and increases the spread of the yellow pigments (lutein or psittacin). Individual feathers over most of a Pearled bird will have more of the yellow family of pigments visible giving them a scalloped pattern.

It is especially interesting to note that males do not retain the Pearled colourings. They soon lose this after their first moult. Though you may not be able to see this pattern, it is not essentially gone. It is only covered up by more grey pigment.[2]

There are a tremendous number of colour varieties (combined mutations), including ADMpied Cinnamon, genuine albino (White(faced) Ino), Opaline Cinnamon (aka Pearled Cinnamon), Palefaced Ino (aka Creamino), Whitefaced Cinnamon, Whitefaced Opaline (Whitefaced Pearl).

The genuine albino (White(faced) Ino) cockatiel is the exact genetic equivalent of any other albino mutation in other parrot species such as the budgerigar, the celestial aka Pacific parrotlet, the Indian-ringnecked subspecies of rose-ringed parakeet, the splendid aka scarlet-chested parrot and the white-eye-ringed lovebird species. Throughout all parrot and parakeet species, the genuine albino mutation is always produced by the visual combination of the genuine blue mutation (otherwise known as the white base gene in African grey parrots and all cockatoo species including the cockatiel) with Sex-linked Ino (and/or exceptionally with non-sex-linked Lino in some species)

Mutations can appear both individually or in a wide variety of combinations such as albino (White(faced) Ino), Pearled Ino (Pearled Lutino), Whitefaced Pied and Opaline-Cinnamon (aka Pearled-Cinnamon). Still fairly hard to find is the rather new yellow-suffusion (incorrectly known as Emerald and/or Olive) mutation. Cockatiels do not actually have green pigment in their plumage, thus yellow-suffusion specimens don't either. The yellow suffusion combined with underlying black (or pure brown in Cinnamon specimens) pigmentation produces an illusion of greenish tones giving rise to the genetically incorrect common names of Emerald for this trait.

Many mutations retain the normal features (black eyes, grey beak, grey feet/skin and black toe nails) of wild-type (grey) cockatiels. However:

Sex-linked mutations such as Cinnamon, Ino, Opaline (Pearl), Pallid (incorrectly known as Platinum) and/or sex-linked yellowcheeks have a higher ratio of female to male offspring due to the mode of inheritance.[3][4][5]

See also

References

  1. ↑ Normal Cockatiel, Native Cockatiel Society of Australia, 2008
  2. ↑ Cinnamon Cockatiels Pearl Cockatiels
  3. ↑ Cockatiel Genetics, Feather Affair, viewed 20 May 2007
  4. ↑ Genetic Terms, Cynthia Kiesewetter, North American Cockatiel Society, 2000
  5. ↑ Cockatiel Color Palette

External links

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