Monday, January 23, 2012

Avian Genetics, Bourke Parakeets by Su Yin

Introducing Su Yin who has commented on this site frequently as "neversink7," and graciously agreed to be a guest blogger on avian genetics. Below follows her post on Bourke genetics.  For your education and enjoyment! 

Bourkes are a delightful grasskeet.  They are the only grasskeet with pink being their main color.  Quiet and friendly with males being excellent singers, it’s hard to resist trying to keep a pair of each mutation!  Often, there are multiple terms that are used to describe the same mutations.  I will try to include the more common ones.
Basic genetic  nomenclature:

Normal or wild color refers to the natural or baseline genetics/coloring of the birds in the wild.  Mutations alter the baseline appearance of the birds from normal/wild colors.

For birds, similar to humans, there are 2 copies of each autosomal chromosome on which the genes exist, so there are 2 copies of each gene.   There are also the sex chromosomes that determine the gender of the bird.  In contrast to humans, the male bird has 2 copies of the same sex chromosome called the Z chromosome (ZZ) and the female bird has 1 copy of the Z chromosome and 1 copy of the W chromosome.  For the mutations that exist on the Z sex chromosome, the male bird can have 2 copies of these mutation genes while the female bird can only have either 1 copy or none.

Another concept that is important to grasp is dominant or recessive.  A gene that is dominant will show up even if only 1 copy of the gene exists in the bird.  If a gene is recessive, there needs to be 2 copies of the mutation gene in the bird in order for the mutation to show up. 

The term “split” applies to the recessive genes when the bird only has one copy of the mutation gene.  Since it doesn’t have 2 copies of the recessive gene, it will not physically show the mutation, but it carries the hidden mutation gene that can still be passed to its offspring.
Common bourke mutations:
Note Normal male at left has brighter colors
than Normal hen on right. © Gail Lewis
The normal Bourke is subtly colorful with grey over the head and back, dusty pink on the belly, yellow scalloping on the black wing feathers.  The males have blue across the brow and the hens do not. Males also have more blue on their wings.
Autosomal recessive mutations:
The genes for these mutations are on the autosomal chromosomes and 2 copies of the mutation gene are required to physically show the mutation.  Both the male and female can be split to these mutations.

Bronze fallow male:        ©Su Yin
Bronze fallow: 
All black pigments are changed to brown shades, eyes are red, skin and nails are pale. The bird generally looks lighter.  The blue band on the brown and wing still exists in the male and not in the hens.  There can be different degrees of darker vs. lighter coloring depending on the strain.

Pale fallow:
Pale fallow male: ©Su Yin
Also called cream or yellow.  All black pigment is changed into light browns, eyes are red, skin and nails are pale.  The color overall is lighter than bronze fallow with more yellow/cream colors.  There can be different degrees of darker vs. lighter coloring depending on the strain.

Pale fallow hen: ©Su Yin

 Photo by Atholl Shelton (Australia).'p/pied%20%20025_jpg_view.htm.

Irregular pattern of absence of deposition of pigment all over the body.

Sex-linked recessive mutations:

These mutations are genes that only exist on the Z chromosome and require 2 copies of the mutation gene in males but only need 1 copy in the females to show up physically.  Since the hens only have 1 copy of the Z chromosome, they will either show or not show the mutation, whereas the males can be split to the mutation if they have only 1 copy of the mutation gene.

The black coloring is brownish colored.  Eyes are dark red.  Nails are horn colored.  No increase in the yellow or cream coloring.
Cinnamon Bourke:

Lutino Bourke     ©Su Yin
Inability to produce any dark pigment, so normally blue areas are white, pale pink over the head and body with yellow coloring over the wings and back.  Skin and nails are very pale.  Eyes are light red.  Males may be a little darker in color, but confirmation of gender requires behavioral differences or DNA sexing.

Opaline males: ©Su Yin
More commonly known as rosy or rosa.  This mutation mainly redistributes the existing colors of the Bourke but enhances the pink/red colors.  Thus the common name of rosy because most birds with this mutation look pink all over.  Some birds can have blue or green in the tail region. 
Through selective breeding, strains of mostly blue or green and other variants have been developed.  These are not different mutations from the opaline, just variations of the same mutation through selective breeding.   Those with a little bit of every color are often called “rainbow.”  Males usually are darker in color while less black/grey on the face, but this is not 100% reliable.  Both genders will have the white stripe on the underside of the wings, which usually only shows up in hens. 

Below are examples of opalines with less pink and other colors. To the left is a blue opaline and the one on right is often called a rainbow.

Blue opaline Bourke.
Breeding and photo from A. Coljon.

Rainbow Bourke.
Photo and bred by A. Coljon.

Combinations of mutations:
When different mutations are bred together, one can develop combinations of the different features.  Included here are only the more commonly available combinations, but let your imagination run wild with the endless possibilities J.

Opaline fallow:
Often called pink, sometimes white-faced pink. These can be developed with combination of the opaline and either the bronze or pale fallow mutations. There is a lot less of the black/darker pigments and eyes are red. Again, males may be darker in their red/pink color with the hens having more white on the face, but this is not confirmation of gender.
Pink hen or opaline fallow hen:        ©Su Yin

Pink male or opaline fallow:       ©Su Yin

Opaline lutino:
More commonly known as rubino.  This is a combination of the opaline and lutino mutations.  The birds are still red eyed with complete lack of darker pigments.  The addition of the opaline gene redistributes the red/pink pigments to a wider area of the body, so the birds tend to be darker pink than lutinos with more pink on their back and wings.  Gender can be very difficult to tell based on appearance alone.

Opaline lutino:          ©Su Yin

A little about me… (Su Yin)
I’ve been a lifelong lover of animals and nature.  I’ve kept different mammals, namely cats and most recently a dog, though I have dabbled in bunnies and mice in the past.  Then there is some venturing into reptiles and frogs, but birds have definitely developed into a passion for me. 
I started with a pair of zebras and now have numerous birds of several species.  I keep various finches and breed some of them.  Gouldians and societies make up the core of my breeding program, but I do also breed stars, owls, shaft tails, and various parrot finches at times.  I also try to breed some of the rarer and very difficult to breed waxbills, but that’s another very long story J. 
I started keeping grasskeets a few years ago.  Once I saw a picture of a scarlet-chested grasskeet, I just had to have a pair.  From there, I acquired turquoisines.  I managed to resist Bourkes until I chanced upon The Splendid Bourke Bird Blog, then saw one in person, and I was hooked.  Recently, I’ve also acquired a couple pairs of elegants.  Just like finches, different species of grasskeets have different personalities, but most are peaceful and make good neighbors for the finches I keep together with them. 
Having a background in the biosciences, I naturally gravitated to the interesting genetics that birds can have and love the challenge of trying to breed quality birds as well as different mutations.  There are books available for reference on the different mutations of various birds, but a lot of information can often be found online – try googling  ;D.  Feel free to check out my birds at:


Anonymous said...

I am a small hookbill enthusiast for 65 years. I am pleased to find such excellent genetic and images info on your site! Thank you! Your commitment and exuberance with the enjoyment of contributing your thorough knowledge to the serious birdbreeder/hobbyist is greatly appreciated!

Anonymous said...

I really appreciate your thorough presentation! I particularly am impressed with the images you provided! You easily encompassed all pertinent subject documentation. Thank you!