Mutations in the psittacine species generally are caused by changes in the melanin and the carotenoid, and only occasionally in the structure color. We therefore can concern ourselves mainly with the changes in melanin and carotenoid. The following are the most usual forms.
In this mutation, the quantity of melanin is reduced. The colors of the wild form are retained in lighter, diluted form--frequently as light, grass-green. The yellow turquoisine parakeet is an example of this mutation.
Lutino, albino, yellow:
In these mutations, melanin is completely or almost completely lacking. In Lutinos and albinos, melanin is absent from all parts of the body---feathers, eyes, beak, feet, and nails. In yellow, melanin is absent only from the plumage. Lutinos and albinos are therefore easily recognisable by their red eyes; normal yellows have dark eyes. Lutinos and albinos differ from each other in that the former still has its carotenoid and, therefore, will show some yellow, orange, and/or red, whereas the latter has lost these colors as well as the melanin colors, leaving a pure white bird with red eyes. For that matter, when melanin is totally absent, the structure color (blue) becomes white.
Here, the melanin is absent from parts of the plumage. The pied mutation usually has a patchy, irregular color pattern, with white or yellow patches where the melanin is absent. There is a great variety of pied patterns, ranging from a few affected feathers to large areas of the plumage. This mutation must not be confused with the results of an inadequate diet. A deficiency of the amino acid lysine in the diet, for example, can result in an inadequate formation of melanin. Thus, some green feathers can become yellow, whereas black ones can become very pale gray to whitish. An improvement in the diet will result in normalisation of the plumage after the following molt. The second mutation in this category is the opaline. Here, the carotenoid becomes more intense. Light yellow becomes deep yellow, medium yellow becomes near orange, and pink becomes near red. The opaline mutation is difficult to recognise, as its outward appearance varies from species to species. In the red rosella, virtually the whole underside and tail are red; red also can be seen in the back markings. The rose Bourke is also a brilliant example of the opaline mutation. The normal yellowish color is replaced by a pure pink, and the melanin is lost in the mantel, back, secondary flight feathers, and head. This arrangement is similar to that of the budgerigar (parakeet), in which the mantel has no markings; in the Bourke this also applies to part of the wings. The pearled (or opaline) Cockatiel shows a totally different variation. Melanin is absent from the center of the feather, so that each affected feather is white or yellow with a dark edge. This gives a checkered effect, seen most often on the wings. The yellow of the pearled is lighter than that of a normal gray Cockatiel. Young Cockatiel males are like normal gray cocks. The back of the neck, mantle, and wings are covered with white or yellow pearly markings. After approximately 6-12 months, the males molt into their adult plumage, being normal gray (wild form). The hens, however, keep their beautiful pearling. Eyes, beak, feet, and legs are as in normal gray.
In these mutations, the color of the melanin is changed: black is replaced by brown. In cinnamons, brown predominates; fallows show a brown-gray that is particularly obvious on the primary wing feathers. These mutations give varying outward appearances, depending on the bird species. The effects are more obvious in a Cockatiel than in a Bourke or a Kakariki. Green becomes lighter in color and more yellowish; gray becomes more brown-gray. An interesting difference between the cinnamon and the fallow is that although the young of both are hatched with red eyes, the cinnamon gets dark eyes within a week and the fallow retains the red eyes. There can, therefore, be no confusion with yellow mutations, which are hatched with dark eyes.
In this mutation, the carotenoid is diminished. The plumage, therefore, shows less yellow, orange, and/or red. In a good sea green mutation, the carotenoid is reduced by half. There are variations. Less carotenoid produces a more bluish bird; more carotenoid gives a greener one. An example is the sea green splendid parakeet.
A pure blue bird has melanin and, of course, the structure color blue. Because carotenoid is absent, yellow, orange, and red tints are totally missing. The white face or charcoal Cockatiel also is included in this group. Here, too, the yellow and red are missing, but because the wild color is not green the mutation produces white rather than a blue plumage.
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