Chapter 9 – Color Mutations
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The study of the genetics of birds is complex, as their colors often are formed in different ways than just through pigments in the feathers and skin. The casual budgie owner interested in breeding a few budgies probably has little interest in the details of avian genetics, so this section will touch on it only lightly. Here you will learn how colors are formed in budgies and a little about a few major color varieties.
A Little Genetics
An animal (or plant, for that matter) inherits its characteristics through genes carried on chromosomes. Chromosomes are strands of DNA that form pairs, when in the cells of the body, and are single strands in eggs and sperm. Each DNA strand carries varying combinations of four amino acids that can pair with another acid on the other strand. These combinations produce proteins or enzymes that control how structures in the embryo will develop and when certain chemical processes will turn on and off. The differences among species are due largely to the sequences of these amino acids.
Budgie breeders have developed a number of color varieties (called mutations), ranging from yellow to green to blue to white, and mixes of colors, too!
Mutations are inherited changes in the DNA, usually the result initially of high-energy rays of some type (such as cosmic rays or radioactivity) or of a strong chemical that changes the amino acid sequence, often by destroying one of the base pairs. If the cell survives the catastrophe, the off spring will carry the same defect. If the defect is not serious, the embryos will live and carry the mutation; when the animals mature, their off spring will have the ability to inherit the mutation as well.
Most mutations are neutral, having little or no effect on how the animal thrives. Many are harmful, preventing the embryo from developing and producing sex cells or preventing the sex cells from joining successfully in fertilization. Some mutations are deadly, killing the embryo in the egg or shortly after hatching. Only a few mutations are good in the sense of helping animals better adapt to their environments and giving them an advantage over other members of their population. For a budgie breeder, however, a mutation is almost exclusively one that changes the nature of the cells that produce the colors of a wild budgie. (In a few cases, it also changes other feather features, such as the development of small crests in some birds.)
Budgie Colors
What follows is a general explanation of how budgies get their different colors. There are exceptions, of course, and it is not possible to cover all the possibilities, so consider the following a primer in budgie coloration.
Although budgies are usually green, blue, or yellow, with black and white accents, there are really only two pigments in the feathers and skin of budgies: melanin, a pigment that causes dark colors such as black and brown; and a carotene layer that produces yellow (varying to red and orange). Variations in color are caused by the way light travels through the carotene layer and is reflected or transmitted by the melanin layer. Carotene is located in the thin, transparent layer at the top of the color cells in the birds' feathers, whereas melanin granules are present toward the center of the cells.
English Budgies
English budgies are very large (often ten inches long or longer), bulky, big-headed budgies. They are popular with some owners who show their birds on a regular basis, and they are occasionally seen in pet stores. They owe their relatively gigantic build mostly to selective breeding over the past century, rather than to mutations. Breeders selected the largest birds of each clutch and then bred them to other very large birds, over and over again through the decades. English budgies show mostly the same color mutations as American (or common) budgies do, and the two can be interbred with no genetic problems.
NORMAL GREEN
In a normal (wild type) green budgie, large amounts of melanin granules are present in the color cells, and the upper layer is translucent yellow from carotene pigments. After sunlight passes through the surface of the cell, the red part of the spectrum is absorbed by the melanin, but the blue wavelengths are reflected back through the surface. In the process, they must go through the yellow pigment layer. Our eyes see blue light filtered through yellow as green. A green budgie, remember, has a lot of melanin plus yellow in the surface layer. But because not all the cells of the body have a similar amount of melanin, we see yellow to yellow-green areas on the normal green budgie.
Budgies won't show all the color possibilities you can see in other birds because their skin and feathers have only two pigments: melanin (dark brown or black) and carotene (yellow, ranging to orange and red).
The green and yellow colors we see in a normal green budgie are the result of the presence of pigments and the way the light absorbs and reflects the colors.
BLUE
In blue budgies, there is a lot of melanin in the cells, but there is no yellow in the surface layer. Thus, when the blue light is reflected back from the melanin, it does not go through a yellow filter, and our eyes see blue. Remember: when melanin is present, yellow is absent.
WHITE
As you might expect, white is the absence of both melanin and carotene pigments, with the upper layer of the color cells filled with reflective white granules. Most light waves pass through the cell, but we see the white of the outer layer. Remember: white lacks both melanin and carotene.
YELLOW
In yellow budgies, there is almost no melanin in the color cell, but the upper layer is yellow. Blue light passes through the cell and is not reflected, so all we see is the yellow of the surface layer. Remember: when melanin is absent, yellow is present.
Genetically Speaking
The presence or absence of the pigments is indicated by a shorthand code when geneticists and budgie breeders write about their birds. As a rule (some systems differ), genes that produce melanin are indicated by O, those that produce yellow carotene by F. A green bird has both O and F genes, a blue only the O, a yellow only the F, and a white neither O nor F. The gene for melanin is carried on the Z (X) chromosome, so a male budgie may have one or two chromosomes with Z (X), a female only one. If the O gene is present in a female, it will be displayed.
As you might expect, these genes exist as dominant and recessive alleles, indicated by upper- and lowercase letters: F is dominant, f is recessive. A green bird might thus be indicated as FO, a blue one as fO, a yellow as Fo, and a white as fo. In reality, the details of inheritance of these simple factors are much more complicated; there are genes that control the intensity of the colors, for instance. Genes also occur in pairs, and one may be dominant and the other recessive.
Because of the complexity of the colors of budgies, it is difficult to generalize about what will happen when you mate two birds of similar or different colors, as the external appearance may not reflect the internal genetics. If homozygous birds are mated, their off spring will be the same color as the parents; if the parents are heterozygous, a variety of different color distributions is possible, according to strict mathematical formulas.
Major Color Varieties
Currently, there are between seventy and one hundred recognized budgie color variations. However, many of these variations are simply differences in shade (dark green, light green) within larger variations (green versus blue, for instance). Another large number of recognized variations are rare and difficult to breed for, being found only at large budgie shows or exhibits. Still another significant number of variations are virtually impossible to distinguish without knowing something about the history of the budgies' parents and their genetics. Only the commonly seen colors are discussed in the following list.
Albinos are all white, with no black (melanin) present in the feathers or skin. They have red eyes. This is a sex-linked mutation that is said to belong to the blue color series (yellow absent). Compare albinos with lutinos (of the green series).
Blues have blue bodies and black and white striping in the wings. The face mask is white. Body color varies greatly, and three major shades of body color (sky blue, which is bright, clean blue; cobalt, which is deep cobalt blue; and mauve, which is a sometimes patchy purplish blue gray) are recognized.
Cinnamons have pale, bright cinnamon brown in place of the black markings on the body and wings, and the brighter body colors are somewhat washed out. This mutation can be bred into any body color. This is a sex-linked mutation said to be of the green color series (yellow is present).
Fallows look a lot like cinnamons, but their shade of brown is darker, often with a bronzy tint. This mutation belongs to the blue series. To tell a fallow from a cinnamon (both can occur in all body colors and result in washed-out blues and greens), look at the eyes. A fallow always has dark red eyes, whereas a cinnamon chick has red eyes for only about a week after hatching; then the iris turns dark.
Greens are perhaps the most commonly sold colors and represent small variations of the colors of wild budgies. The face mask is bright yellow (white in blues) and the body feathering is a shade of green. Three shades are recognized by most breeders: light green, dark green, and olive green.
Lutinos are basically albinos belonging to the green color series. They are entirely yellow and have bright red eyes and red skin on their ceres and legs. Unlike albinos (who are white), lutinos don't all belong to the same mutation; there are sex-linked and non-sex-linked lutino mutations that appear identical externally. Together, lutinos and albinos are sometimes called inos.
Genetic Terms
Genetics is a complex science, and it has developed a complicated vocabulary to allow its practitioners to express themselves clearly. Although you will end up using few of these basic terms, you certainly will run across them if you delve deeper into budgie genetics.
· Allele: one of the two different versions of a gene at the same position on the chromosome strands. Usually one allele is dominant, the other recessive.
· Dominant: a "strong" gene that overruns its weaker corresponding gene, the gene for green is dominant over the gene for blue.
· Genotype: an individual's actual genetic makeup, as opposed to what is visible externally. · Heterozygous: a situation in which the genes controlling a character are different: one gene is dominant, and the other gene is recessive.
· Homozygous: a situation in which both genes controlling a character are the same, either both are dominant or both are recessive.
· Phenotype: an animal's external appearance, as opposed to its genotype. Lutinos, for instance, are yellow birds, but several different genotypic combinations can produce birds who are externally identical.
· Recessive: the "weaker" gene of a pair controlling the same feature. Blue is the recessive of green.
· Sex-linked: a trait carried on the chromosome with the genes that control sex. Male budgies have two large chromosomes (referred to as Z in birds and X in mammals), whereas female birds have one large Z (X) and a smaller W (Y) chromosome. The genes for some colors are found only the Z chromosome, so if a gene for a particular color occurs on the Z chromosome of a female, she will display that color. Albino and cinnamon are common sex-linked color mutations.
Opaline budgies have a V-shaped color design on their backs between their wings, and they don't have the fine, dark, curved feather edges seen in most other types of budgies. Opaline can occur as both blue and green variations and is sex-linked.
Violet is an interesting mutation rarely seen, in which a gene intensifies the blue coloration to a deep violet shade.
Yellow is another seldom-seen mutation because it is difficult to breed in a clean-looking form. Yellows look much like lutinos but differ in their genetics, and they often show patches of green feathering against the yellow.
This chapter only scratches the surface of the color mutations of budgies, but it should be clear that these are exceedingly variable birds. More color variations are "discovered" all the time, and the number of technically different colors may be almost unlimited.
Basic Mutations
The following list presents almost two dozen of the major categories of color mutations (and one feather mutation) in budgies, as recognized by many breeders. Not all are externally distinct, and some include several shades within their definitions. Albino, Blue, Cinnamon, Clearflight, Clearwing, Crested (a feather mutation), Dominant (Australian) Pied, Fallow, Gray, Green, Greywing, Lacewing, Lutino, Opaline, Rainbow, Recessive (Danish) Pied, Red-eyed Lacewing, Violet, Yellow, Yellowface
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