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Head Color - Inheritance in Gouldian Finches (Chloebia gouldiae) by: Robert Clark and John Wilson (NFSS - May/June 1998) Much of the difficulty in understanding the inheritance of head color in Gouldians results from the expectation of a clear hierarchy of dominance. Unfortunately such a pattern doesn't exist. The actual expression of head color is more along the lines of the children's Rock, Paper, Scissors game. Black covers yellow and red covers black, but yellow covers red. Were the relationships even this simple little if any confusion would remain and repeated efforts to clarify, such as this would not be needed. The glossary and definitions that follow reflect an effort to simplify the subject or at least cut it into bite-sized pieces. The genetics terms that follow are the same ones used in describing the inheritance of body color. Glossary of Terms
Genotype:
genetic make-up of the individual. Sex Linkage Because the genes for red head color are sex-linked and one of these genes is required for the expression of yellow head coloration, a clear understanding of sex linkage is necessary to understand the inheritance of both red and yellow head traits. By definition, sex-linked traits are carried on the male sex chromosome (X-chromosome), while other traits are carried on autosomal chromosomes. This is a very important distinction. All autosomal chromosomes are carried in pairs by birds of both sexes. Male birds carry two sex (X) chromosomes and female birds carry only one sex (X) chromosome. This is exactly opposite to the situation in mammalian genetics. In Gouldian males, where two (X) sites are available , inheritance is similar to autosomal inheritance. In females, there is a single (X) site , and any gene present will be fully expressed when present as a single copy, whether co-dominant, recessive, or dominant. As an example, a yellow hen carries a single co-dominant gene for yellow back color yet fully expresses yellow back, not dilute back. It is simplest to describe the mechanism of Gouldian head color inheritance by referring to the black headed bird as the normal state and noting the effect on the black headed bird when it inherits one or more genes for red head or yellow head. All possible head color combinations can be described by this method without the added confusion of black headed inheritance. The actual mechanisms by which head colors are produced is described below. Chemistry and Mechanisms Research data has shown that melanin is the only pigment involved in head coloration in black headed Gouldians. Canthazanthin (a beta-carotenoid) is the only pigment present in the head feathers of red headed Gouldians, while lutein epoxide (an alpha-carotenoid) is the only pigment present in the head feathers of yellow headed Gouldians. The distinction of alpha and beta carotenoids is important since it strongly implies that red and yellow headedness are truly separate traits with completely separate metabolic pathways for head pigmentation, rather than one simply being a derivative of the other. There are additionally very distinct differences in the feather structure on the heads of black headed versus red or yellow headed birds. Specifically, the barbs are flattened and lack barbules in areas of pigment in the red or yellow headed birds, presumably allowing for better presentation of the color. This finding strongly suggests a second (structural) gene at play in the determination of head coloration. It would also suggest that either this second gene is tightly linked to the gene determining red head color, or alternatively, that this gene is suppressed by the genetic black head. Head color Black head is the most prevalent Gouldian head color in the wild, and probably represents the original Gouldian head color. Black head is inherited as a sex-linked recessive to red head. Many prefer to think of this as the absence of any head color modifier genes. Red head inherits as a sex-linked trait, dominant over black head. Males may carry none (black head), one (SF red head) or two (DF red head) genes for red head. Since these genes are carried on the male (X) chromosome, the hen carries only a single copy of the gene. Hens may carry none (black head) or one (red head) gene for red head. Because the single X chromosome of a red headed hen must carry the red head gene and will be passed to every male offspring, all male offspring of a red headed hen will also be red headed, unless they also inherit two yellow head genes (yellow head). An easy means of remembering this relationship is that all black headed males have black headed mothers. The reverse of this statement is: red headed mothers produce all red headed or yellow headed sons. Red headed males can produce offspring of all three head colors depending on the genotypes involved. Yellow head is most easily thought of as a double or combination mutation, even though that has been shown to be not precisely correct (see Chemistry & Mechanisms). The yellow head mutation inherits as an autosomal recessive trait requiring two genes for expression, but also requires the presence of at least one red head gene in order to be expressed. Offspring from yellow headed pairs may be black headed (with yellow beaks) hens only, (note this only occurs when the male is SF for red head) or yellow headed (cocks and hens) when the male is DF for red head. From the above description it becomes apparent that either sex may carry a single yellow head gene without its expression. This is a hallmark of recessive inheritance. For a bird to be black headed, it must carry the black head gene on all its X chromosomes (1 for the hen, 2 for the cock). However, a bird may be a phenotypic (visual) black head while also being a genetic yellow head. These birds carry two yellow head autosomal genes while also carrying black head genes on their X chromosomes. These birds will, however, have yellow-tipped beaks. Black headed birds that are heterozygous for yellow head will have red-tipped beaks, as will those that aren't carrying a yellow head gene. A bird which carries a single red head sex-linked gene will always be a visual red head unless also carrying two autosomal recessive yellow head genes, in which case it will be a phenotypic yellow head. To obtain a yellow headed Gouldian, the bird must be both genetically yellow headed (carrying 2 yellow head genes), and must also be a "genetic" red head. Both sexes may be heterozygous for yellow head without expressing any visual evidence of this state.
Gouldian Finches -Yearly Routine JANUARY
When my birds are almost through the moult, I take them off canary seed
and leave them on hungarian and jap millet, and some green feed such as
cabbage, spinach, celery and lucerne (alfalfa) FEBRUARY
You should have eggs by the end of FEB. As soon as young
You will be in full swing with plenty of young coming out of the MARCH I do not like to move my young as I find that any upset at this time of their lives is likely to bring on a form of entro-hepatitis. All attempts to isolate the real cause has not been successful as yet, but the symptoms are always the same and of all the young gouldians I have done post mortems on Iwould say that 75% have died from one cause. The signs are always the same. On wetting the dead bird in a dish of sodium hypochlorite and parting the feathers along the sternum you will be able to see the mustard coloured flesh on opening the bird along this line., you will see that the flesh is quite yellow in colour and any fat around the vent and crop area will be a bright yellow in colour. Whole grain will be seen in the droppings and on opening up the gizzard you will find that the lining of the gizzard has come away and is a bright yellow colour. MAY
By
the end of May you should be thinking about ending your breeding JUNE to OCTOBER Maintain same feeding programme NOVEMBER
I
start to reduce the intake of canary seed very slowly and by SOME PROBLEMS FOUND IN GOULDIANS ENTERITIS Treat the whole flock with Chlortetracycline (eg) Aureomycin Tricon 3 days on treatment 4 days off for three weeks and clean up the aviary with a good germicide like sodium hypochloride (bleach) and followup the treatment with Vitamin B Complex. BALD HEADS
There may be more than one reason for this condition but one I am sure
is a too vigorous male. Not many gouldian breeders ever see MINERAL BLOCKS
DO
give your gouldians blocks especially made
for these birds and on NO account give them rock salt to eat. They love
salt and will soon beome addicted to it which in turn will ruin their
livers and kidneys. If salt is available to these birds they will
always be seen pecking away at the salt and will develop a pasty white
diarrhoea and ERNIE NINNESS Scientific name: Chloebia gouldiae PHYSICAL CHARACTERISTICS:Length: 130-140mm, or 5-5½". There are three distinct color variations among the Gouldian Finches: the red-headed, the black-headed, and the yellow-headed. The variations of color are predominantly evident on the heads of the finches. Though these were once thought of as differing species, it is realized now that the variations are clearly linked to color alone. All three color variations couple randomly, and are found intermixed in the same geographic areas. The variations are as follows: The red-headed male has mostly green wings fringed in brown. Its posterior and upper tail feathers are blue with the remaining tail feathers being black. It has the distinctive red cheeks, lores and forehead depicted by its name, with the top of its neck baring a fleck of black which is traced in blue. The chest is a light purple, edged with a narrow orange-yellow streak. Below the chest the remaining portion of the abdomen is lush yellow, and beneath the tail is a splash of white. Its grayish-white beak is curiously tipped with red. The yellow legs and feet are typical. Its eyes are deep brown. The male black-headed form (as is evident in its name) only varies from the red-headed form concerning head, lores, cheeks, and ear-coverts which are black. Similarly, the yellow-headed male form is yellow in these same areas. Like many finches, the Gouldian has a stout parrot like bill. Its two medial tail feathers are long, ending in a point. The color variations of the this finch tend to be its most striking characteristic. This is true both in color vitality, and in the way the edge of one color is clearly defined from the next as though artificially applied. The difference between sexes seems to be typical when considering many species of birds, in that the females are less pretentious due to the lackluster or drabness in their coloring. This might be considered a mating related difference, so that the male can more easily attract females. Another interpretation concerning color variation might be affixed to survival of the brood; the brightly colored male might attract the attention of a potential predator, thus luring it from the nest. The juveniles are also recognizable due to color differences. Their heads, sides and necks are ashy-gray, changing to an olive green on the backs, wings and tail feathers. These have underlying brownish-black feathers which are fringed in a yellowish tone, and have inner feathers that are a burnished white. The under-surface of their bodies are an ash-brown, paler on chin, middle of the breast and under the tail feathers. The upper portion of the beak is blackish with cream colored bumps, while the lower portion is reddish-white and tipped red. Their legs and feet are light brown, and the eyes are brown. DISTRIBUTION and HABITAT:Gouldian Finches occur in tropical northern Australia from about Derby to the eastern side of the Gulf of Carpentaria to around the area of Charters Towers. This species appears to be migratory throughout its range, moving more southerly in the rainy season and reappearing in the northern regions for the dry months. The numbers of Gouldian Finches have drastically decreased since the onset of the twentieth century, and they are very rarely found east of the Gulf of Carpentaria. The Gouldian Finches natural habitat is the tropical savannah woodland. They select open plains with dispersed groups of tall trees, or the fringes of mangroves and thickets, and tend to always be near water. BEHAVIOR:Gouldian Finches are apprehensive birds generally evading populated areas. A relatively quiet bird, the Gouldian has a high pitched call that can not be heard over long distances. They have hisses, clicks and weakened whines for their songs. There is an occasional sharp modification of the normal call when startled. Additionally, there is an intimate call when in the nest that sounds like a foundling's wiwiwiwi. During the courtship ritual the male commences with beak-wiping, bobbing, showing off his brilliant colors by ruffling his feathers and holding his body and tail erect. At the same time he expands his chest and fluffs the forehead feathers. The female will often do a bit of beak-wiping during the ritual. Much of the courtship takes place on a limb, sometimes followed by copulation in the nest. Both parents brood over the nest during the day, and the female sits the eggs at night (unless in captivity, then both are seen brooding during day and night). There is always one parent with the nest, they relieve one another with the nesting call. Additionally, the care of the young is carried out by both parents. The Gouldian is a hole nester, using termite mounds and hollow trees as sites for their nests. The nest tend to simple with no roof, thin walls and may even be found in tall grasses. The nests are generally near water. They usually breed in the second part of the rainy season, when there is plenty of food such as grass seed and insects. Gouldian Finches are extremely social birds. They continue social life even when breeding, and even share hollowed out segments in the same tree. They are often found in flocks of several hundred. DIET:Gouldian Finches are not ground feeders and favor foraging from upright grasses. Semi-ripe to ripe grass seeds are a major part of the Gouldian Finches' diet. They also eat a variety of insects including beetles, termites, flies, flying ants, and spiders along with their prey right from the web. They drink by sucking. REPRODUCTION and GROWTH:Gouldian Finches bear up to three broods in succession, amassing 4 to 8 eggs per clutch. Though they bear more young, they do not seem to have higher numbers than other grass finches. This may be due to their vibrant coloration, and the likelihood that this makes them easy prey. Newly hatched, the Gouldian foundlings have no fleece and are bare until approximately the 12th day when their primaries begin to protrude. They leave the nest at three weeks and begin their first molt at about 6-8 weeks, Molting can last for several months and sometimes can extend into first year's early courtship activities. The molt may also be delayed until the end of breeding activities. Some breed while still being fed by their parents, which may indeed increase their breeding capabilities. This is helpful especially because the Gouldian Finch experiences a high rate of predation.
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