Birds have additional cones in their retina which allow them to see ultraviolet colors that are invisible to humans. A new study from Yale University has revealed that, when it comes to colors that are visible to birds, hummingbirds have a plumage diversity that exceeds the known colors of all other bird species combined. The experts report that their discovery increases the total of known bird-visible plumage colors by 56 percent.
Professor Richard Prum is an ornithologist who has spent years studying the nanostructures that give birds their colorful plumage. He was surprised by what he found in hummingbirds.
“We knew that hummingbirds were colorful, but we never imagined that they would rival all the rest of the birds combined,” said Professor Prum.
For the investigation, study lead author Gabriela Venable collected data on the wavelengths of light reflected by feathers from 114 species of hummingbirds. This data was compared with colors found in 111 other bird species, including parrots and penguins.
Based on what they know about the visual abilities of birds, the researchers were able to identify plumage colors as seen by the birds themselves.
“Coloration has many functions in the lives of animals, including sexual and social communication, crypsis, aposematism, thermoregulation, and more. The phenomenon of animal coloration involves a cascade of physical and biological events beginning with the transmission of ambient light through an animal’s habitat and incident on its body, interacting with pigments and optical nanostructures in the animal integument, and reflecting back into the environment,” wrote the study authors.
“The sensory component occurs when this light is transmitted through another individual’s eye and is absorbed by ocular pigments, leading finally to a perception of color. The field of sensory ecology encompasses research on all aspects of this cascade of phenomena.”
The colors found in hummingbirds include saturated blues, blue-greens, and deep purples that are most variable on the animals’ crowns and throats. These parts of the body play a key role in mating displays and social interactions.
“Watching a single hummingbird is pretty extraordinary,” said Professor Prum. “But the combination of versatile optical structures and complex sexual displays make hummingbirds the most colorful bird family of all.”
The study is published in the journal Communications Biology.
By Chrissy Sexton, Earth.com Staff Writer