The science of Cockatiel Parakeet's colour genetics deals with the heredity of colour variation in the feathers of the species known as Nymphicus hollandicus, commonly known as the 'Cockatiel'. About fifteen primary colour mutations have been established in the species and enable the production of many different combinations.
Note : aka stands for also-known-as, cka stands for commonly-known-as ika stands for incorrectly-known-as
The multiple names for these mutations is due in part to different regions of the globe naming the same colour change a different term. This does not mean that it is a different mutation. It only means it is a different name.
Colour mutations are a natural phenomenon equally occurring in captivity and in the wild.
The "Normal Grey" or "Wild-type" 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 the bird.
"Whiteface" cockatiels have their yellow pigments deactivated by an autosomal recessive gene, resulting in a cock with a truly white face and a hen with a more typical mottled grey face. This means, there is no yellow or orange colouring in a whiteface cockatiel.
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. While mature males always display solid white coloured undersides of tail-feathers.
Unfortunately, a good number of Cockatiels of all Ino mutations and varieties (Albino ika Whitefaced Ino, Palefaced Ino aka Creamino, Lutino, Opaline-Ino aka Pearlino, etc.) are usually affected with a transmittable genetic flaw monstrously enlarging the bald-spot below the crest, due to intense overbreeding and a general lack of breeders to breed it out.
"Pied" cockatiel plumage patterns vary significantly from animal to animal, giving rise to cockatiel breeders and hobbyists' "heavy pied" and "light pied" loose distinctions. Unfortunately, the degree in piedness remains virtually unpredictable genetically. However, breeding heavily pied specimens together generally produces a higher percentage of heavily pied offsprings than breeding lesser pied specimens together. Ultimately, the "pied" mutation causes the bird to lack a majority of the typical gray 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.
It is important to know that, throughout Parrot species the ADMpied (AntiDiMorphic Pied) gene negates the male's ability from ever displaying his species' sexual-dimorphic features. Leading to ADMpied cockatiels being notoriously difficult to sex visually but being excellent examples for studies in genetic traits. However, in Mono-Morphic species (i.e. Conures, Lovebirds, Macaws, Rosellas) 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.
Cinnamon and Opaline ("Pearled") mutations are sex-linked recessive. In Cinnamons, the melanin pigment is modified in such a way that eumelanin pigments are stopped at the brown stage of their development to becoming black. Here is an excellent description of the pearled cockatiel:
The Pearl Cockatiels gene does not have any visual affect 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 (psittacins). 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 molt. Though you may not be able to see this pattern, it is not essentially gone. It is only covered up by more grey pigment.
There are a tremendous number of colour varieties (combined mutations), including ADMpied Cinnamon, Albino (ika Whitefaced Ino), Opaline Cinnamon (aka Pearled Cinnamon), Palefaced Lutino (aka Creamino), Whitefaced Cinnamon and Whitefaced Opaline (Pearl).
The Albino (ika Whitefaced Ino) Cockatiel is the exact genetic equivalent of any other Albino combination mutation in other Parrot species such as the Budgerigar, the celestial aka Pacific Parrotlet, the Indian-ringnecked aka Rose-ringed Parakeet, the splendid aka Scarlet-chested Parrot and the white-eye-ringed Lovebird species. This mutation is always produced by combining the genuine Whitefaced mutation (otherwise called Blue mutation in all Lories, Lorikeets and/or typical Parrot species) and Complete Albinistic (either NSLino and/or SL Ino) mutations together.
Mutations can appear both individually or in a wide variety of combinations such as Albino (ika Whitefaced Ino), Pearled Lutino (aka PearlIno), Whitefaced Pied and Opaline-Cinnamon (aka Pearled-Cinnamon). Still fairly hard to find is the rather new Yellow-suffused (ika 'Emerald and/or 'Olive') mutation. Cockatiels do not actually have green pigment to their plumage, thus Yellow-suffused specimens don't either. The yellow suffusion combined with underlying black (or brown in Cinnamon specimens) pigmentation produces an illusion of greenish tones giving rise to the genetically incorrect common names of 'Emerald and/or 'Olive' 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, ;
Fallow and Ino mutations have pink to red eyes, pink feet, clear (pink) toe nails and pinkish-white beaks.
Cinnamon specimens look quite alike the Wildtype (aka Normal Grey) specimens, with the exception of being pure-brown where Wildtypes are grey.
Sex-linked mutations such as Cinnamon, Ino, Opaline, Platinum (ika 'Pallid') and/or SL-Yellowfaced have a higher ratio of female offspring to male due to the mode of inheritance from parents to offspring.