The Edged Fischer's Lovebird

The Genetics of Colour in the of Budgerigar and other Parrots

This page created 7th March 2001

The Edged Fischer’s Lovebird

[Agapornis fischeri]

by Dirk Van den Abeele

The first edged Fischer's were born in the Netherlands near the end of the 1970s. I do not know of another single mutation Fischer's that has caused so many questions, doubts, and speculations, than these edged birds. And even now considerable misunderstanding about this mutation exists. The number of enquiries we receive monthly about this subject is high. Many breeders stop breeding these birds and that is to be regretted. It is a beautiful mutation with a lot of possibilities. I will try by means of this article to make everything a bit more comprehensible.

The facts: co-dominant inheritance

This mutation has an autosomal co-dominant inheritance. It is caused by a melanin reduction in the feathers. Important differences exist between the phenotypes of single factor and the double factor edged bird *. But these differences may also show up when comparing two single factor birds. Add to this that the pastel mutation (50% dilution of melanin) also has been bred in and you will understand that a lot of confusion is possible. The differences however are clear, we will list them below:

[* for convenience from now on SF = single factor, DF = double factor.]

In case of a co-dominant inheritance one bird only is sufficient to obtain offspring of the same phenotype. In contrast with recessive mutations, birds can never be split for a dominant one. Simply put; a bird either shows the dominant mutation or it does not have it at all. So never buy a Fischer's/edged; it does not exist!
It is possible to breed the edged mutation into all existing colours; birds with a melanin reducing mutation exceptied. Breed them only into light green, dark green, olive green, blue, cobalt and mauve birds. Do not breed them in combination with pastel (50% melanin reduction) or ino (100% melanin reduction). Pastel and ino edged birds lose all distinguishing signs of being edged - there is no contrast left - and should not be bred for exhibition purposes. A golden rule: any mutation combination that does not clearly show the specific outlook of each of the combined factors is useless. Breeding of these indistinguishable combinations should be discouraged strongly.
The fact that the mutation is co-dominant can give us SF and DF birds. How come? Genetic information is found in or on chromosomes. These chromosomes come in identical pairs (with one exception) called chromatids in both the male or the female bird. At fertilisation a male chromatid links to a female chromatid and the pair is complete again.

Together they form a complete set of chromosomes. In other words: the chromosome pairs of a young bird are made up by one chromatid of the sire and the complementary chromatid of the dam. Consequently a chick gets 50% of its genetic information from the sire and 50% genetic information from the dam. Suppose the sire passes on a chromatid with a dominant mutation and the dam does not. One chromatid of the chick will carry this mutation: it is single factored. Should both parent pass this dominant gene evidently the youngster will be double factored.

To visually represent this a simple drawing will make things clearer. (This system can be used for many dominant mutations)

We draw 2 squares representing a set of chromosomes of the male. The male is single factor, so we darken one of the squares. Given that the hen also is single factor we draw a similar second set of squares. They are numbered from 1 to 4. Knowing that always half the chromosome set of each parent is passed on to the offspring this gives us 2 x 2 = 4 possible combinations:

Father		Mother

1	2	3		4
			1 + 3 = DF

			1 + 4 = SF

			2 + 3 = SF

			2 + 4 = Normal

In summary, the pairing of a SF Edge to a SF Edge will produce:

¼	= 25%	DF birds
¼+¼ = ½	= 50%	SF birds
¼	= 25%	Normals

These percentages are nearly exact when say 100 young are produced. The sequence in which the three phenotypes appear is a question of luck however: you may get four DF birds in the first nest, or four SF ones, or four Normal ones, or any combination of DF, SF, and Normal.

To make it even clearer, I'll give a scheme below showing all pairing possibilities:

SF Edged	X	Normal	gives	50% Normal 50% SF Edged
SF Edged	X	SF Edged	gives	25% DF Edged 50% SF Edged 25% Normal
DF Edged	X	Normal	gives	100%SF Edged
DF Edged	X	SF Edged	gives	50% SF Edged 50% DF Edged
DF Edged	X	DF Edged	gives	100% DF Edged

So far we have used Edged without referring to a body colour. When using colours one first has to consider what the colour combination will become and in a second step link the Edged factor to these results.

First; consider a Dark Green paired to another Dark Green (both birds have one dark factor):

Dark Green

gives

25% Light Green
50% Dark Green
25% Olive Green

Second; add the 1 : 2 : 1 ratio of the SF Edged X SF Edged pairing to each colour:

6¼%	Light Green	12½%	SF Edged Light Green	6¼%	DF Edged Light Green
12½%	Dark Green	25%	SF Edged Dark Green	12½%	DF Edged Dark Green
6¼%	Olive Green	12½%	SF Edged Olive Green	6¼%	DF Edged Olive Green

Single factor Edged birds

Now that we have some more insight in the mode of inheritance it is time to take a closer look at the basic forms of this mutation in both green and blue birds. It has already been stated that this mutation is caused by a melanin reduction, but also that differences exist between the phenotypes in this mutant. Not all SF Edged birds show the same markings; the melanin reduction sometimes differs in various body parts. Therefore we should try to breed birds with a maximum of contrast. That means a melanin reduction of 50% on the body and the wing coverts; the latter will show somewhat darker of course. In SF birds the males usually show the clearest pattern: of course from time to time better coloured hens also show up.

In the best specimens we see that the feathers of the wing coverts centrally are diluted, while the edge of the feather retains its original colour. This causes the Edged effect. The dilution in these best specimens is around 50%. This makes the central part of the feather ‘very light green’, almost yellowish. In blue birds this becomes a ‘very light grey’. Primaries and feet keep the original colour. The rest of the body is an evenly diluted. Because of this dilution the possession of a dark factor becomes difficult to see in a green bird; it shows better in a blue one. The facial mask is unaltered both in form and colour since the pigment here is mainly psittacin, which is unaffected by a melanin mutation.

In lesser marked birds we notice that the melanin reduction is often considerably less (usually in hens) and that results merely in slightly faded birds. These birds are extremely difficult to recognise as being Edged. This has in the past been the cause of the rumour that split Edged birds existed. These birds are however useful as breeding stock, but absolutely not as exhibition birds.

It is a wise decision to start with a DF bird. Then you are assured that all offspring are SF and mistakes are excluded.

It has often happened that even ‘Big Names’ have mistaken, and even sold, a pastel light green for an Edged light green. I give them the benefit of the doubt whether this has been a deliberate mistake or not. But the difference is easy to see.

A pastel light green should ideally have a 50% melanin reduction all over its body. The body colour is diluted, but so are the primaries. They have to be light grey. In too strongly diluted birds they even may become a ‘dirty white’. In the Edged birds the primaries are still almost completely black.

Double factor Edge birds

This phenotype is very easy to recognise. DF Green birds become dirty yellow with light grey primaries and still show marking near the edge of the wing and on the upper part of the wing coverts. The facial mask tends to decrease a bit but should have the same size and colour as the light green bird. The colour of the feet has hardly changed.

DF Blue birds are very clear bluish or greyish birds showing a white mask and the same marking on the wings as in green. Here, too, the colour of the legs has hardly changed. Pastel birds split ino can be excessively diluted too but they always have white primaries and the wing colour is patchy, not evenly coloured.

The name Edged

Originally and as usual several names were given to this mutation, varying from ‘Richard’ to ‘Edged’. Even now when speaking of DF birds people use ‘Golden’ or ‘Golden cherry’ (green series) or ‘Silver’ and ‘Silver Cherry’. Adding a precious metal to the name of a bird almost automatically increases its monetary value. Suffused has been in use too, but suffused is a recessive mutation caused by a 80 to 90% loss of melanin. Edged inherits dominantly.

Another link is to the spangled budgerigar. This is indeed a dominant mutation causing a melanin reduction too. But the visual differences are obvious. Maybe we'd best put them in a table:

Spangle Budgerigar		Edged Fischer's
Primaries: completely bleached, particularly the centre.		Primaries: almost unchanged compared to a Light Green.
Tail feathers: bleached again		Tail feathers: unchanged
Feet: flesh coloured		Feet: greyish
Feathers of wing coverts: the black melanin in the centre has moved towards the edges. The edges are black. The centre becomes yellow (in green birds) or white (blue birds)		Feathers of wing coverts: the centre of the father is bleached, either a diry yellow or a dirty grey-blue; the edges retain the original feather colour.(speaking of SF birds)

It stands to reason that the name spangle is a serious misnomer. The use of Edged is the only logical one.

In our nomenclature (the naming system adopted by the BVA) we speak of:

SF or DF Edged Light Green

SF or DF Edged Dark Green

SF or DF Edged Olive Green

SF or DF Edged Skyblue

SF or DF Edged Cobalt

SF or DF Edged Mauve

We discourage the breeding of Edged Pastel, or Edged Cinnamon or Fallow birds: the beautiful contrast will be lost.

That still leaves us enough possibilities with this mutation. How about a SF Violet (a real Violet is a Cobalt with at least one violet factor) for instance? Prices in Europe have dropped to a reasonable level so many breeders can afford to buy these birds. The first edged Masked have already appeared on stage.

The BVA negotiates with foreign associations to standardise colour names. A sound base for this nomenclature is a link to feather structure and changes in the pigments present compared to the wild coloured bird. International contacts can only improve if each party knows what the other is talking about.

My thanks to Dirk for permission to feature this article on a variety which is not yet very familiar or well understood. Dirk’s peronal Webpages are at:

Agapornis Page

You will also find much of interest at the Belgian Lovebird Society (of which Dirk is the Chairman) Webpages:

Belgian Lovebird Society

http://birdhobbyist.com/parrotcolour
e-mail: CliveHesford@compuserve.com