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Warning: All rights reserved. This article appeared in the issue of the National Finch and Softbill Society Bulletin. Volume 21. No. 4. July/Aug. 2004. (p. 6-7). Anyone wishing to reproduce this article for another bulletin, newsletter, article, journal, CD, or any other public forum needs express written consent of the NFSS and of the author michael@exoticfinches.com

The spunky and beautiful horse, Smarty Jones, lost the Triple Crown by coming up ten feet short after running 7,920 feet at Belmont. This may have cost his owner tens of millions of dollars in stud fees although he will do just fine with that much less. He is expected to be mated with about 200 mares a year and earn tens of thousands for each romantic encounter. Coming in second at a finch show on the other hand has little impact on one’s finances and probably just as little on the winning bird’s sex life! If I count labor, utilities, vet bills, and supplies, I’m losing just as much money after winning 7 best in shows then I did when I just began. So, unlike horses, when you breed birds it is pride in your achievements that is the major reward. That being said, it is very frustrating if, after six or seven generations, your birds look the same as they did when you started and your show results are still more dependent on luck than skill.

I have decided that a series of short articles discussing breeding methods and the genetics surrounding them might be helpful to those wanting to advance their lines with the goal of producing top notch birds with some consistency. Installment one will be brief and lay the foundation for future articles.

In order to discuss breeding, the following terms should be understood. I will add a bird example in parentheses if it helps explain the definition. Future articles will assume you know these terms or at least have access to them.

Gene – the physical unit of heredity consisting of a DNA sequence on a specific location on a chromosome.

Allele – an alternative form of a gene often expressed symbolically by a letter or abbreviation.

Locus (pl. loci) – the specific location of a gene on a chromosome.

Genotype – the sum total of the genetic makeup of an individual.

Heterozygote – in birds we often call these “splits”. A one-locus genotype containing functionally different alleles (e.g. Aa, rather than AA or aa).

Homozygote – a one-locus genotype containing functionally identical alleles (e.g. AA, or aa).

Hybrid – an individual that is the product of a pairing between two species, or breeds within a species, or lines within a breed.

Phenotype – the observed category of a trait (e.g. the appearance).

Simply-inherited trait – a trait affected by one to a few genes.

Qualitative trait – a trait in which genotypes can be expressed in clear categories (e.g. chocolate:chestnut:fawn, in other words traits that are “either/or”).

Quantitative trait – a trait in which phenotype shows continuous numerical expression (e.g. size, weight).

Quantitative trait locus (QTL) – a locus that affects a quantitative trait.

Polygenic – a trait affected by many genes with no single gene having the overriding effect.

Linkage – the occurrence of two or more genes of interest located on the same chromosome.

Sex linkage – a gene located on a sex chromosome resulting in an inheritance pattern that is different from genes located on non-sex chromosomes (autosomal) and consequently different in males and females.

Mutation – the process that alters DNA to create new alleles.

Dominance – an interaction between genes at a single locus such that in heterozygotes one allele has more effect than the other. The allele with the greater effect is dominant over its recessive counterpart.

Partial dominance – when the expression of a heterozygote is intermediate to the expression of the homozygotes. The male dilute Gouldian (split for yellow body) is an example.

Epistasis – an interaction among genes at different loci such that the expression of a gene at one locus is dependent on the specific alleles present at one or more other loci.

Line – a group of related individuals within a breed.

Line breeding – the mating of individuals within a line.

Purebred – wholly of one line (i.e. not crossbred).

Inbreeding – the mating of close relatives.

Outcrossing (or outbreeding) – the mating of unrelated individuals.

Backcrossing – the mating of an individual to any other individual with which it has one or more ancestral breeds or lines in common.

Hybrid vigor (or Heterosis) – an increase in the performance of hybrids over purebreds or inbreds most noticeably in traits like fertility and infant survivability.

Inbreeding depression – the reverse of hybrid vigor.

Half sibs – half brothers or sisters (i.e. they share a parent).

Test cross – a mating designed to reveal the genotype of an individual.

Prepotency – the ability of an individual to produce offspring like itself and especially uniform.

Pleiotropy – when a single gene affects more than one trait.

Closed population – a population that is closed to the introduction of genetic material from outside populations.

Reference

Bourdon, R.M. 2000. Understanding Animal Breeding (2nd ed.). Prentice Hall, Upper Saddle River, New Jersey.

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