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Tortoise Shells
Discussion on the Tortoise Shell Color


By: Bob Christman
GENERAL COLOR DEFINITION
An internet dictionary defines tortoise shell as follows:
1. the hard, mottled, yellow-and-brown shell of some turtles and tortoises, used in inlaying and, especially formerly, in making combs, frames for eyeglasses, etc.
2. a synthetic substance made in imitation of this
3. a mottled, yellow-and-brown color pattern
4. any of several common, black and yellow-brown butterflies (genus Nymphalis) with markings resembling those of tortoise shell
5. a cat with a mottled coat of black, brown, red or yellow, white, etc.

In Wests a tortoise shell is the intermixture of different shades of bronze, grizzle and white on a kite based bird.

TORTOISE SHELL STANDARD DESCRIPTION
MARKINGS - Base color to be splashed somewhat evenly with grizzle and white throughout head, neck, chest, body, and wingshield. Flights, tail, and muffs colored and interspersed with grizzle or with grizzle and white.
COLOR - Bronze Tortoise Shell (Grizzle Bronze Blue). Head, neck, chest, and body to be bronze, interspersed with grizzling and white and may be flecked with dark gray-blue, dark bronze, and dark/blackish kite. Flights, tail, and muffs to be either dark blue-gray saturated with bronze or kite, and interspersed with grizzle or grizzle and white. Tail may show a tail bar. Beak dark horn and eye ceres grayish. Beak may be stained.

The standard description for tortoiseshells does not address the percentage of white versus color that should be present in a tortoiseshell (something that definitely needs to be addressed in next standard revision). Because the standard doesnt specify amount of white that can be present it leaves this evaluation to the discretion of the judge.

EVALUATION OF COLOR AND MARKINGS
The following evaluation outlines the parameters that most knowledgeable judges and tort breeders appear to be judging to and breeding to.

The tortoiseshell color is the result of an intermixture of rich bronzes, dark kite, grizzling and white. It is how well these colors interplay with each other that determines how striking the tortoiseshell color is. If a tortoiseshell is too white or too dark it loses the impact of the interplay of those colors that make a tortoiseshell what it is. A mostly white tort with a few colored feathers or a tort with only a few white feathers in the head do not exhibit that good mixture of rich bronze, dark kite, grizzling and white that make up the good tortoiseshell color. A light tort needs to have enough color and a dark tort needs to have enough white so that they express that interplay of colors that makes for a good tortoiseshell color. A mostly white tort with a few colored feathers or pepper headed dark tort (white or grizzling in the head only) can not be good tortoiseshells, irregardless how nice the bird is otherwise, because they do not exhibit that good mixture of rich bronze, dark kite, grizzling and white that make the good tortoiseshell color.

Bird 1 is an example of a tortoise shell that is too light. There is not enough color on this bird to express a good tortoise shell color/marking. This amount of white would be considered to be a major fault.

Bird 2 is an example of a light tortoise shell. Though this bird has a lot of white it still has enough color in the wingshield to express good tortoise shell color/markings. This bird would be considered to have good color/markings. A little more white and the judge would have to consider it a minor fault. A whole lot more white and the judge would have to consider it a major fault.

Bird 3 is an example of a dark tortoise shell. Though this bird is mostly colored in the wingshield it still has enough white to express a good tortoise shell color/markings. This bird would be considered to have good color/markings. A little less white and the judge would have to consider it a minor fault. A whole lot less white and the judge would have to consider it a major fault.

Bird 4 is an example of a tortoise shell that is too dark. There is not enough white on this bird to express a good tortoise shell color/marking. This little amount of white would be considered to be a major fault.

Acceptable color and markings for a good tortoise shell should fall somewhere between those of Bird 2 and Bird 3 in the photos above.

GENETIC MAKE UP
Genetically tortoise shells in Wests are grizzle kites. Kites are the result of a combination of kite bronze and blue T-pattern. The richer more bronze looking kites have other factors enhancing their color. One gene for recessive red enhances the bronze color. Most of the better kites also seem to carry the dirty factor. Grease quill also typically enhances the color in the kites by adding good luster. Many of the kites also are sooty. Whether sooty enhances the kite bronze is not known for sure but it at least does not seem to be detrimental. In addition there are probably other unknown factors also enhancing the bronze appearance. All the factors that enhance the bronzing in the kites also appear to enhance the color in the tortoise shells.

BREEDING TORTOISE SHELLS
Tortoise shells are commonly bred by mating tortoise shells to kites or by mating tortoise shells to tortoise shells. Because the better colored kites and tortoise shells carrying recessive red, they will also produce red selfs and red mottles. Most torts lighten (increase in amount of white) when molting from their juvenile plumage to their adult plumage. In contrast there is a smaller number of torts that darken (decrease in amount of white) when they molt to their adult plumage. I suspect that the torts that darken with the molt are sooty and those that lighten with the molt are not sooty. Sooty birds typically darken noticeably with their first molt and continue to darken with age.

Suggested matings in order of preference:
Medium tort to medium tort
Light tort to medium tort
Light tort to dark tort
Light tort to kite
Medium tort to kite

Dark tort to dark tort and dark tort to kite matings should normally be avoided. These matings typically seem to result in mostly more dark torts.

Some breeders prefer the tort to kite matings. I prefer the tort to tort matings especially the medium tort to medium tort matings because I seem to get a higher percentage of properly marked torts from this mating then any of the others.

Torts can also be raised from red selfs and red mottles (that came from tort matings) to torts. However I would not recommend that mating because 1) it is not possible to evaluate how good the color is for torts because the color is hidden under the recessive red and 2) you will most likely raise an even much larger percentage of recessive reds.



 Bob Christman
Tortoise Shells
Discussion on the Tortoise Shell Color


 
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