GENETICS FOR AVICULTURISTS: New US. Cockatiel Mutation and its Genetic Nomenclature

Abstract

N ews of an apparently new mutation in Cockatiels has riveted avicultural circles, enthralling color breeders everywhere across the United States. The new mutation, or mutations, also appear to have a modifying effect upon existing color varieties as did the Whiteface mutation some 15 years ago. Whether it is an individual spontaneous mutation, or recombinant form, i.e., cross mutation(s), remains to be proven through detailed, vigorous and objective record keeping. However, those who can afford the new variation are now acquiring the birds, and as with any new variety in demand, the supply is limited and prices will be high for some time.

Understandably, not much is actually known about the new mutation either in its genetics or mode of reproduction. Yet, its effect on longtime color breeders has been invigorating. The problem, however, with writing about a possible new mutation is that until all the facts are in, only theory may be offered. Unfortunately, such facts may take years to accumulate and there is no easy "quick fix." However, the comments offered below will perhaps shed some light on the subject and will hopefully he construed as helpful, until more is known. Certainly, additional facts and new information will have a direct bearing on how we later evaluate this possible new mutation and what it will he called.

American Standard

An attempt is currently being made

 

by some U.S. breeders to assemble an American Standard of Nomenclature. The goal is to construct a list of genetically correct labels (i.e. nomenclature) to name mutations which will be applicable to all species of birds. For example, a Fallow mutation will be called a Fallow, whether it occurs in Cockatiels, Budgies, parrots, or any other species of bird. This effort is long overdue and even the order in which the mutations are listed will be organized.

For Cockatiels, the national specialty societies, such as the American Cockatiel Society and the National Cockatiel Society, will have excellent input into such an effort. It is crucial that aviculture select the correct nomenclature (recognized by aviculturists both· nationally and internationally), in order to avoid the errors and confusion which have occurred in other species of birds, especially with the increase of new mutations on the rise.

Genetics

In avian genetics it is generally understood that green carotenoids are not present in the structural colors of birds. Rather, bright green may be produced when a particular carotenoid pigment first aids in the absorption of short-wave radiation from white light, and scatters the remaining light in the end of the color spectrum allocated for green. The dull and olive green colors are usually produced by an interaction between melanin and xanthophyll pigments.

 

A common occurrence in avian color mutations is the process of schizochroism, or split color, as in the sense of "cloven." This is not to be confused with the avicultural term "split," or the geneticist's term heterozygous. In some birds, schizochroism may occur involving two different pigments which may overlay one another within the same feather.

A schizochroic mutation could account for both the lighter phase of the new U.S. color and the darker (or dark factor) variants. It is tempting to speculate that perhaps xanthophylls may be underlying (or overlying) melanin pigments, e.g., phaeomelanin (brownish pigment) which, when coupled with normal light scattering in structural colors, produce the appearance of green. Theoretically, such pigmentation could be responsible for the partial olive green appearance in some of the new U.S. mutations which are especially dramatic when viewed in direct sunlight.

Color Pigmentation

There has been some speculation that the new U.S. mutation may he the result of a Dilute. Unfortunately, the term "Dilute," or dilution, is poorly understood among aviculturists as is the mechanism of schizochroism. Geneticists generally have a stricter definition of the term "Dilute," which requires a bird to exhibit an even reduction in the quantity of pigment, resulting in a marked reduction in color intensity throughout the body. (The key to dilution is the uniform reduction in both the quantity and intensity of all color pigments present.)

While any bird 'may be affected by dilution, the definitive clue is that all colors and patterns are still present, but in faded condition. While one might wish to debate the point in the lighter colored birds, a dilute factor does not appear to significantly effect the yellow or orange carotenoids in the face, crest, or cheek patch, in either the lighter or darker varieties. Rather than appearing significantly faded as would be expected, the intensity of the yellow mask and orange cheek patches appear to be similar to their Normal Gray counterparts.

Another mechanism which should

 

not be discounted is the possibility of color modifiers, more specifically, adherent colors. Such changes can occur from either pigmented, or unpigmented substances laid on top of feathers. There is not much known about this mechanism in scientific circles but there are many references among aviculturists, the author included, when explaining some alterations in color mutations.

The definitive solution to the problem of correctly identifying the new mutation will come when formal analysis is rendered by examining feathers from all the variant colors under the microscope. This is more difficult than it sounds, as the only qualified individuals are molecular geneticists and properly credentialed scientists with a Ph.D. in genetics, rather than aviculturists. There are also very few avian veterinarians who have further training and credentials in molecular genetics, since genetic research is usually focused on more lucrative markets as dogs and cats (e.g. hip dysplasia, etc.). Currently, attempts are being made to seek out such trained, credentialed scientists, as any other researcher would lack the knowledge, professional training and impartial bias to fully understand or interpret the results.

Meanwhile, it is critical that all aviculturists working with these birds keep detailed, accurate records so that data can be compiled which may shed some light on the mode, (or modes), of reproduction. The author is also starting to work with these birds and is willing to act as a central "clearing house," to receive data from other breeders which will be compiled and distributed to all who participate in the long-term study.

 

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References

American Budgerigar Society. Standard of Perfection. Revised, 1991. USA.

Bastiaan, T., Bastiaan, G.J.J. Ringnecked Parakeets and Their Mutations. 1995.

Farnsworth, M.W. Genetics. 1978. Harper & Row. New York, New York.

Hart, Ernest, H. Budgerigar Handbook, 1970.

T.F.H. Publications. Jersey City, New Jersey.

Rubin, Linda, S. 1996, Recent Mutations in Cockatiels, Convention Proceedings, 1996 American Federation of Aviculture, Concord. California. USA.

Rubin, Linda, S. 1997. "Recent Mutations in Cockatiels in the USA." First International Cockatiel Symposium, Native Cockatiel Society of Australia, Sydney, Australia.

Rutgers, A. Budgerigars in Colour. Blandford Press Ltd. London, England. 1967.