Budgerigar colour genetics: Difference between revisions

Content deleted Content added

Inline

Revision as of 19:02, 9 March 2007

The science of budgerigar colour genetics deals with the heredity of colour variation in the feathers of the species of the parakeet known as Melopsittacus undulatus, commonly known as the 'budgerigar parakeet' or 'budgie '.

Background

The basic colour of the wild budgerigar is green. The feathers of most green birds, including budgerigars, contain both a yellow pigment and a darker pigment called melanin. When these feathers are exposed to a white light source, such as sunlight, only the blue part of the spectrum is reflected by the melanin. This reflected light passes through the yellow pigments, resulting in the green colouration known as Light Green.

The many colour variations of budgerigars, such as blue, yellow and albino, are the result of mutations that have occurred within specific genes. There are at least thirty-two known primary mutations that can influence budgerigar colour. These can combine to form hundreds of secondary mutations, which may or may not be stable. These specific variations in gene types are called Alleles. For example, when referring to the gene that decides feather colour, the allele might be 'dominant green' or 'recessive blue'.

As is true with all animal species, identical colour mutations occur in captivity as do in the wild. This has been demonstrated when captive-bred budgerigars have developed very rare mutations that had only been previously recorded amongst wild populations.

Classification of mutations

Basic groups

Each of the thirty-two primary mutations belong to one of the four basic groups of mutations classified in parrot species genetics;

Albinism : where eumelanin is reduced in all body tissues, either partially or fully.
Dilutism : where eumelanin is partially reduced in the feathers.
Leucism : where all pigmentation is reduced in the feathers.
Melanism : where eumelanin is increased in the feathers.

Dominance relationship

These mutations are inherited through one of the following dominance relationships.

autosomal-Co-Dominant (A-Co-D),
autosomal-Complete-Dominant (A-C-D),
autosomal-Incomplete-Dominant (A-I-D),
autosomal-recessive (A-R),
autosomal-Poly-Genic (A-P-G)
Sex-Linked-recessive (S-L)

Table of primary mutations

Name	Common name	Type	Allele/Locus	Inheritance
Dark Factor		Blue Loci	D-Locus	A-Co-D when only Blue Loci alleles, else exclusively/additionally A-I-D
Blue		Blue Loci	bl*bl	A-Co-D when only Blue Loci alleles, else exclusively/additionally A-R
Blue II		Blue Loci	blII-Locus	A-Co-D when only Blue Loci alleles, else exclusively/additionally A-R
Yellow Faced Blue		Blue Loci	blII*yf	A-Co-D when only Blue Loci alleles, else exclusively/inclusively A-R
Golden Faced Blue		Blue Loci	blII*gf	A-Co-D when only Blue Loci alleles, else exclusively/inclusively A-R
Crest Factor		Structural	Cr-Locus	A-P-G
Dark-Factor		Structural	D-Locus	A-I-D
Grey Factor	Dominant Grey Factor	Structural	G-Locus	A-C-D
Grey Factor	English Recessive Grey Factor	Structural	g-Locus	A-R (extremely rare or extinct)
Grey Factor	Australian Recessive Grey Factor	Structural	ag-Locus	A-R (extremely rare or extinct)
Violet Factor		Structural	V-Locus	A-I-D
Suffused	Dilute	Dilutistic	dil*dil	A-Co-D when only dil-Locus alleles, else exclusively/inclusively A-R
Clearwing		Dilutistic	dil*cw	A-Co-D when only dil-Locus alleles, else exclusively/inclusively A-R
Greywing		Dilutistic	dil*gw	A-Co-D when only dil-Locus alleles, else exclusively/inclusively A-R
Anti-dimorphic (ADM) Pied	Danish pied, Recessive Pied, Harlequin	Local-Leucistic	s-Locus	A-R
Piebald	Australian Pied	Local-Leucistic	Pb-Locus	A-C-D
Pied	Continental Dutch Pied, Clearflighted Dutch Pied	Local-Leucistic	Pi-Locus	A-C-D
Spangle Factor		Total Leucistic	Sp-Locus	A-I-D
Dark-eyed Clear		Total Leucistic	dilcw / dil**gw	A-Co-D (not a genuine primary mutation, it is produced by ADM Pied plus Dutch Pied)
NSL Albinism	Recessive Albinism	Albinistic	a-Locus
NSL Ino	Recessive Ino	Albinistic	a*a	A-R (extremely rare or extinct)
Bronze Fallow	German Fallow	Albinistic	a*bz	A-Co-D when only a-Locus alleles, else exclusively/inclusively A-R
Brown, Brownwings	Sepia	Albinistic	b-Locus	Presumed A-Co-D when only a-Locus alleles, else exclusively/inclusively A-R (extremely rare or extinct)
Cinnamon	Cinnamon Wings	Albinistic	cin-Locus	S-L-R
Dun Fallow, Grey-Brown Fallow	English Fallow	Albinistic	df-Locus	A-R
Faded		Albinistic	fd-Locus	A-R (extremely rare or extinct)
Beige Fallow, Pale Brown Fallow	Australian Fallow	Albinistic	pF-Locus	A-R (possible)
Plum-eyed Fallow	Scottish Fallow	Albinistic	pl-Locus	A-R (possible)
SL-Albinism		Albinistic	ino-Locus
SL-Ino		Albinistic	ino-Locus	S-L-R
SL-Clearbody		Albinistic	ino*cl	SL-Co-D when only ino-Locus alleles, else exclusively/inclusively S-L-R
BlackFace		Melanism	bf-Locus	A-R
Darkwings		Other	dw-Locus	A-I-D (extremely rare or extinct)
Dominant Clearbody		Other	Cl-Locus	A-C-D
Opaline		Other	op-Locus	S-L-R
Saddleback		Other	sb-Locus	A-R (extremely rare or extinct)
Slate		Other	sl-Locus	S-L-R

History

In the first few decades of the 1900s, especially in-between World Wars I and II, the keeping and breeding of the budgerigar had become very popular all around the world. Consequently, various mutations occurred and were soon established during this period.

Time line

1870-75 The very first registered sudden captive-bred colour mutations were Green Suffused (aka Dilute Green), Green Greywings and either one of the two types of Lutino (NSL-Ino &/or SL-Ino) mutations. All three occurred in aviaries in Great Britain or Europe. Of these three mutations, only the Suffused Green (aka Dilute Yellow) has survived. This was easily reproduced in great numbers and is nowadays very well established. The first Lutino mutation quickly vanished but it was re-established in Europe some time between 1931 and 1933.

1878 The first Sky Blue budgerigar appeared in Belgium.

1880-85 The Blue mutation suddenly occurred in continental Europe, most probably in Uccle, Belgium. Surprisingly, this variety was not imported in England until 1910.

1915 Simple Dark-Green (aka Dark-Green) in France.

1916 Double Dark-Green (aka Olive) in France.

1918-25 Greywings Green and Greywings Blue appeared in England and continental Europe.

1920
- Crest-Factor in Australia.
- Suffused Blue (aka Dilute White) in England and France.
- Simple Dark Blue (aka Cobalt) in France.

1921 Double Dark Blue (aka Mauve) in France.

1930
- Simple Violet-Green (aka Violet Factor) in Australia.
- The first Clearwing appeared, developed by H. Pier in Sydney.

1931
- Cinnamon in England, Australia & Germany.
- An unknown type of Fallow in California, U.S.A. This soon vanished.
- The German Fallow in Germany, recently been genetically classified and identified as the Bronze Fallow (aka Brown Fallow).
- A plum-eyed mutation, similar looking to Fallow mutations, occurred in England. This vanished or at least became very rare. This mutation was most probably the Brownwings, one of the rarest colour mutations of the species.
- The first Albino specimens were produced in both England and continental Europe.

1932
- Three Fallow mutations occurred in England which became known as the English Fallow. In Australia these have been genetically classified and identified as the Dun Fallow or Grey-Brown Fallow (aka Australian Fallow). The Beige Fallow or Pale-Brown Fallow has been classified in South-Africa, but no reference seems to be available on this particular mutation.
- A the recessive Anti-dimorphic Pied (aka Danish Pied) in Denmark.
- A Dominant Pied (aka Australian Pied) in Australia.

1933
- Green Clearwing (aka Yellow Wing) and Dominant Grey-Factor appear in Australia.
- Both the NSL & the SL Lutino gene occurred in England and continental Europe.
- Three Opaline mutations occurred. An Opaline Green hen was captured in the wild and sold to S. Terril in Adelaide. It was later-on reproduced and is most probably the ancestor of all Opaline specimens in Australia. Two sudden captive-bred Opaline mutations occurred in England and Holland.

1934 Recessive Grey Factor in England.

1935 The Yellow Faced Blue and Golden Face dBlue occurred in several locations.

1939-46 Clear-Flighted Dutch Pied in Belgium.

1948
- Texas Clearbody (aka SL-Clearbody) in the U.S.A.
- Dominant Clearbody in the U.S.A.
- The first Cinnamon-Ino crossover (aka Lacewings) mutation was produced in Australia.
- The first Dark Eyed Clear variety was produced in Belgium by combining the ADM Pied (aka Danish/Recessive pied) with either one of the two Dutch Pied varieties.

1970-74 Single Factored and Double Factored Spangled specimens were produced in Australia.

1975 Saddleback specimens were produced in Australia.

Notes

It is probable that the Greywings mutation survived as the ancestor of all actual Greywings. However, it is possible that the mutation laid dormant in asymptomatic mutant specimens until it was re-established between 1918 and 1925. Blue Greywing specimens were produced later on in 1928.

It is very likely that all Suffused mutation specimens and their varieties are descendants from the first captive mutant specimens. This means that Suffused is the oldest sudden captive-bred colour mutation of the budgerigar species.

References

Martin, Terry (2002). A Guide To Colour Mutations and Genetics in Parrots. ABK Publications. ISBN 0957702469.
Hayward, Jim (1992). The Manual of Colour Breeding. The Aviculturist Publications. ISBN 0951909800.

External links

@@ Line 14: / Line 14: @@
 Each of the thirty-two primary mutations belong to one of the four basic groups of mutations classified in parrot species genetics;
+[[Image:Albino_parakeet.jpg|thumb|right|Because of [[albinism]] this budgerigar has white [[pigment]] and red eyes.]]
 *[[Albinism]] : where [[eumelanin]] is reduced in all body tissues, either partially or fully.
 *[[Dilutism]] : where eumelanin is partially reduced in the feathers.