Zebra Finches Sex & Colors

Sex-Linked Chromosomes

• Chromosomes of male finches are labeled ZZ and females are labeled ZW. In finches, females carry the sex-linked genes. The genotype of an individual refers to the complete genetic makeup of that individual: dominant, recessive and sex-linked genes. Phenotype refers to what is visible, or shown. Certain color characteristics are carried on the sex-linked genes only. Therefore, when a female passes a sex-linked chromosome to her female offspring, the phenotype will show the trait. Sex-linked colors include fawn, chestnut-flanked white and light-backed.

Dimorphism

• Zebra finches have different color characteristics based upon the sex of the bird. This trait is called dimorphism. Male zebra finches tend to be more colorful or more vividly patterned than females. Orange cheek patches is a male-only characteristic, as is a black bar on the chest and a chestnut-colored flank that is spotted white. Male zebra finches have a black-and-white-striped throat, which gives the zebra finch its name. Males also have deep orange-red beaks in contrast to light orange of the female beak.

Color and Pattern Mutations

• Male finches sport more mutations than females. One mutation causes the cheek patch to be black instead of orange. Another mutation results in a bird that is pied -- which means the bird has white patches in its colored areas. Other mutations result in black-breasted or orange-breasted finches. Some of the gene mutations are recessive, so they will not be shown on every bird that carries the gene. However, when the recessive gene is present, there are other characteristics that suggest the presence of the gene. One of the main telltale signs is elongated white flank markings instead of white spots.

Split Gene Characteristics

• Split genes refers to birds with genotypes that include both a dominant and a recessive gene for a particular trait. When this occurs, the dominant gene is shown, but offspring of the bird with split genes may show the recessive characteristic if the other parent of the offspring also carries the recessive gene. Pied is a recessive gene as is chestnut-flanked white.