Birds boast some of the most vibrant colors among land animals. The tropics are often known for the brightest birds, but American birds also display a wide range of striking hues.
But how colorful are our bird friends?
USA TODAY analyzed over 500 photographs of bird species provided by Macaulay Library at Cornell Lab of Ornithology, whose extensive media collection helps researchers identify and study color anomalies and rare bird colors. The species were chosen based on data from Project FeederWatch, a citizen science program run by Cornell Lab, which allows people to submit sightings of birds they’ve seen locally.
Using a machine learning algorithm, we determined the dominant color of each bird photo.
Let’s take a look at the American kestrel, one of the smallest and most colorful falcons in the United States. It can be seen all over the country, hovering over open spaces while looking for insects to eat. Running the photo through a machine learning algorithm resulted in this color palette for the bird.
The machine learning model determined that the dominant color of this bird is dark gray, meaning that this color group contained the most pixels. We ran the same analysis for all 559 bird species, resulting in a rainbow of colors representing American birds.
It is important to mention that the dominant color we got depends on the lighting of the photo, the time of year it was taken, the gender of the bird and its age.
Bird colors do more than just captivate human observers. They also serve utilitarian purposes, indicate overall environmental quality, and play an important role in a bird’s survival and courtship behavior.
“Birds are environmental guardians,” said Allison Shultzassociate curator of ornithology at the Natural History Museums of Los Angeles County in California.
“The artist in me is what really fell in love with bird colors,” Shultz said, “but it was the biologist in me who discovered why they’re so important and that they’re actually worth studying.”
How do birds get their colors?
Understanding bird coloration combines biology and physics. There are two primary ways that birds get their coloration: pigmentation and the physical structure of the feather – sometimes a combination of both.
Pigments are the chemical substances in animal and plant cells that give color, absorb and reflect certain wavelengths of light.
Birds acquire certain pigments, such as carotenoids, by eating fruit, seeds or insects. Carotenoids produce the bright reds, yellows and oranges seen in birds, and they are the same pigments that give carrots and pumpkins their signature color.
The second way birds get their appearance is through structural colors, which result from the interaction of light with the microscopic structures of the feathers. Small air bubbles in the feather refract and scatter light, creating vivid colors that we can perceive.
Imagine the surface of a soap bubble or a rainbow-like oil slick. These phenomena, along with the brilliant blue wings of morph butterflies, are examples of structural color at play.
The northern cardinala classic red bird, has pigments in its feathers that absorb all but the red wavelengths, which are then reflected back to us.
Carotenoid-based colors are often used as an indicator of a male bird’s quality, Shultz said. Brighter colors are often associated with superior genesstronger immune system and higher reproductive success.
This concept, known as “redder is better,” reflects the idea that brighter birds make better mates, said Richard Prum, an evolutionary ornithologist who teaches at Yale University. But Prum disagrees, saying the concept is a problematic way to “take beauty in the world and turn it into utility.”
While several North American birds exhibit distinct green plumage, turacos, native to sub-Saharan Africa, stand out as the only birds that are really green. Unlike other species, turacos owe their color to a copper-based pigment called turacoverdin.
The common grackle and many iridescent hummingbirds display irises like how a prism splits light in a rainbow. Their iridescent feathers change color depending on the viewing angle, adding to the allure.
Colors of a bird
While bird species dazzle with countless colors, a single bird usually has several colors itself, which our color palettes above do not capture.
The colors that birds have boil down to evolutionary trade-offs and selective pressures, Prum said.
The strongest pressure is what drives a bird’s feathers to be a certain way, Shultz said, whether it’s to impress a mate, blend in with the environment or stay cool in a warm place.
Although bright colors can be good for social and sexual signals, they are not as useful for avoiding predators.
Bright pops of color tend to signal colors used for social interactions. It can be a way of saying: “Join my flock. We are members of the same herd,” said Prum.
For this reason, these vibrant spots often appear on a bird’s crown, neck or breast — areas that encounter other birds, Shultz said. A bird’s back is usually darker and more cryptic, which helps with camouflage. This adaptation, known as countershadinghelps the bird blend in and avoid drawing attention to itself.
Male ruby-crowned kings, for example, may flash a scarlet crown when excited or keep it hidden when necessary.
Feathers containing melanin are stronger, Shultz said, which is why birds often have dark wing feathers to help them in flight.
Do the colors change?
Even within the same species, the color can vary according to age, season and sex.
Birds undergo molting, the process of shedding old feathers and growing new ones, which can result in color changes. Most birds experience an annual molt, usually after the breeding season, Shultz said, but species such as American goldfinches replace their feathers twice a year.
“If you look at birds during certain times of the year when they’re molting, they can look a little wonky,” Shultz said. “It’s just because they’re growing new feathers.”
Molting helps the birds maintain optimal feather condition for flight and allows them to replace worn feathers and remove parasites, Prum said.
Young birds can also look different from their older counterparts. This is because it takes time for birds to signal sexual maturity. Most songbirds reach this state after a year, but sea eagles can take as long as five years to achieve full adult plumage.
Males and females can have different appearances – a phenomenon known as sexual dimorphism. Females tend to be boring because they have different ecological and social behavioral needs, although the two sexes sometimes look identical, as can be seen in the blue jay.
How do birds see colors?
As colorful as birds are to the human eye, we are actually “color blind with respect to birds,” Prum said. That’s because birds see an even wider spectrum of colors than humans can.
“Birds live in a much more vibrant and colorful world than we do,” Shultz said.
Humans have three types of cones in our eyes for red, green and blue light. Birds have an extra type of cone that allows them to see ultraviolet light.
In addition to seeing a wider range of colors, birds can also detect finer differences between them. This means that birds can distinguish subtle nuances in shades of green that are not noticeable to us.
“Everybody always asks me, ‘Can you make bird glasses?'” Shultz said. “And really we can’t because our brains just aren’t wired to neurologically process that kind of information.”
Curious to learn more about the birds you’ve seen in this story? Click on a color to find out.
Contributes: Javier Zarracina
Sources: US Fish and Wildlife Service National Digital Library, Getty Images.
Method: Photos were manually selected to find images of birds in a similar pose, with good lighting and for overall quality. The background was removed from all images and each photo was run through the K-means algorithm to obtain the dominant color. K-means works by dividing the colors of a bird into distinct groups, or “clusters” to find the most representative colors. Each pixel’s color is then assigned to the nearest cluster center. The cluster with the most pixels becomes the dominant color.
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