Scientists Find the Key to a City Bird’s Hue

A pigeon’s style is determined by three genes.

Biologists at the University of Utah showed how three pigment genes interact to cause a variety of colors among rock pigeons. From left to right: The first feather is blue-black because all three genes are normal. The second feather is dilute blue because the Tyrp1 and Sox10 genes are normal but the Slc45a2 gene is mutant, which dilutes the intensity of any color. The third feather from the left is ash-red because of a mutant Tyrp1 gene and normal Sox10 and Slc45a2. But if Slc45a2 also is mutant, the feather color is diluted to ash-yellow (fourth from left). The fifth feather from the left is red because the Sox10 gene is mutant, which overrides whatever color Tyrp1 normally would dictate. Photo Courtesy of Eric Domyan/University of Utah Photo: Photo Courtesy of Eric Domyan/University of Utah — Biologists at the University of Utah showed how three pigment genes interact to cause a variety of colors among rock pigeons. From left to right: The first feather is blue-black because all three genes are normal. The second feather is dilute blue because the Tyrp1 and Sox10 genes are normal but the Slc45a2 gene is mutant, which dilutes the intensity of any color. The third feather from the left is ash-red because of a mutant Tyrp1 gene and normal Sox10 and Slc45a2. But if Slc45a2 also is mutant, the feather color is diluted to ash-yellow (fourth from left). The fifth feather from the left is red because the Sox10 gene is mutant, which overrides whatever color Tyrp1 normally would dictate. Photo Courtesy of Eric Domyan/University of Utah

By Simone Scully

Contributor

Published February 07, 2014

Pigeons are the epitome of the urban landscape, one of only a few species that thrive in a concrete jungle. They tend to come in hues that blend with the gray surroundings, but some are shockingly colorful—crimson, hazel, even gold.

A new study decodes the genes that can determine what makes a pigeon common gray or rare primrose. The research, published in Current Biology,reveals that it comes down to mutations in three specific genes linked to plumage, which are parallel to the genes associated with skin pigmentation in humans.

Using DNA extracted from blood and feather samples collected at pigeon shows in Utah, the scientists found specific variations in the trio of genes. A mutation in the first gene, called Tyrp1, which gives a bird a blue-black hue, paints a pigeon ash red or cinnamon brown. A mutation in a second gene called Sox10, which is recessive, results in red, regardless of the effect of Tyrp1. Differences in the third gene determine whether the shade of a pigeon’s color will be intense or dull.

“In humans, mutations of these genes often are considered ‘bad’ because they can cause albinism or make cells susceptible to UV (ultraviolent sunlight) damage and melanoma because the protective pigment is absent or low,” said Eric Domyan, a biology postdoctoral fellow from the University of Utah, who authored the paper. He explained that in pigeons the genetic differences are innocuous. A mash-up of mutations in these three genes results in 82 different pigeon breeds.

The new finding proves that a plain city bird is not so plain after all.