Scientists ID why Gouldian Finches Have Red, Black, or Yellow Heads

By Pat Leonard
June 17, 2019
Gouldian Finches are incredibly colorful birds native to Australia and widely kept as pets. They can occur in three different color forms. Illustration by Megan Bishop. Gouldian Finches are incredibly colorful birds native to Australia and widely kept as pets. They can occur in three different color forms. Illustration by Megan Bishop.

From the Summer 2019 issue of Living Bird magazine. Subscribe now.

Research led by the Cornell Lab of Ornithology and the University of Sheffield in the United Kingdom revealed an evolutionary selection mechanism that causes polymorphism (multiple color types of a single species) in Gouldian Finches. The study, published in April in the journal Nature Communications, identified the mechanism that allows this species to produce individuals with red heads, black heads, and yellow heads.

“Most people have heard of natural selection,” says lead author Kang-Wook Kim at the University of Sheffield. “But ‘survival of the fittest’ cannot explain the color diversity we see in the Gouldian Finch. We demonstrate that there is another evolutionary process, balancing selection that has maintained the black or red head color over thousands of generations.”

The researchers independently zeroed in on the gene found on the Gouldian Finch sex chromosome that regulates melanin to produce either red- or black-headed finches. Rather than competing, the two teams decided to join forces and share their data. For the yellow morph, a different gene not located on the sex chromosome is controlling the head pigmentation, but that gene hasn’t yet been found.

Study coauthors David Toews and Scott Taylor, who worked on the research as postdoctoral researchers at the Cornell Lab, had done similar previous research that revealed the genes likely governing the plumage differences between Blue-winged and Golden-winged Warblers. One of those gene regions is in the same spot on the sex chromosome that differs among Gouldian Finches with different head colors.

Gouldian Finches—Australian songbirds that have become popular for captive breeding as pets—occur in three morphs for head color. A team of scientists isolated what was happening at the genomic level to cause the different head colors. Graphic by Megan Bishop.Gouldian Finches—Australian songbirds that have become popular for captive breeding as pets—occur in three morphs for head color. A team of scientists isolated what was happening at the genomic level to cause the different head colors. Graphic by Megan Bishop.

“The probability that we’d locate the exact gene region that governs plumage differences in both the Gouldian Finch and the two warblers was almost zero,” says Toews, who is now a professor at Penn State University. “But now that we’ve done it, it opens up the possibility that the same region in other species may also be controlling plumage color.”

Reference

Kim, K.-W., et al. (2019). Genetics and evidence for balancing selection of a sex-linked colour polymorphism in a songbird. Nature Communications 10:1852.

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