Birds are among the most colorful of animals, evolving mainly as an adaptation for reproduction. Males of species such as hummingbirds, sunbirds and t tanagers attract mates with their colors and Red-winged Blackbirds establish and defend territories with their blazing epaulets. And of course, in the thickness of tropical forests, the range of spectacular colors lets all of the birds know who’s who. Other birds, for protection, have evolved disruptive coloration, patterns that break up their outline, such as banded plovers, and birds like nighthawks and bitterns have evolved camouflage.
Feather colors are formed by either or both pigment and structure. One pigment, melanin, produces colors from black to dull yellow; carotenoids are responsible for yellow to yellow-orange colors; and porphyrins produce bright colors in several shades of pink, red, yellow, and green. Structural colors are produced by the refraction of light through the cells of the feather. If you find a Blue Jay or bluebird feather and hold it in your hand, it appears blue because the incoming light is refracted as it is reflected. But if you hold the feather up to the light, the light is transmitted through the feather, itwill appear brown due to the melanin granules. Iridescent colors of hummingbirds, sunbirds, and others are produced in a similar way and the angle at which the birds are viewed causes the colors to vary. Green colors are often produced by a yellow pigment deposited on top of structural blue.
Beginning birdwatchers often consider color to be the best clue to identification, being misled by the common names of birds. One would tend to look for the orange of the Orange-crowned Warbler or the blue of the Tit when the orange crown is not at all obvious and the Blue Tit is not all blue. Color perception also varies with different lighting conditions, so patterns, silhouette, behavior, and habitat are often better clues than color. Seeing color is a bonus.
But because colors are so important and so obvious a feature of birds, many of their scientific names reflect their color or color patterns. The all-white White Tern is Gygis. alba, Alcippe brunnea is the mostly brown Dusky Fulvetta, and Lonchura melanea, the mostly black Sooty Munia. The Blue-Black Kingfisher is aptly named Todiramphus nigrocyaneus. Or the name may reflect the color of only a particular part as in the Little Tern, Sternula albifrons, with a white forehead; Oriolus chlorocephalus, the Green-headed Oriole; and the Cobalt-winged Parakeet, Brotogerus cyanoptera. There are many names that refer to color and use the color prefix like alba-, white, and are used repeatedly for different body parts. Hence we have albicapilla (white-haired), albicauda (white-tailed ) , albiceps(white-headed),, albicilla(white-tailed), albicollis(white-collared), albifrons(white-forehead), etc. and xantho, yellow, as in xanthogastra (yellow belly), xanthocollis (yellow collar), xanthophrys (yellow eyebrow), etc.
The color descriptions are primarily based upon the plumage of the mature male of the species, but we often find mismatches between the descriptive scientific and common names. The Crescent Honeyeater’s scientific name, Phylidonris pyrrhopterus means red or flame-colored wings when the bird’s are actually bright yellow. The Yellow-rumped Warbler’s specific epithet of (Dendroica) coronata refers to its crown, not its rump. The Black-billed Cuckoo’s scientific name, Coccyzus erythropthalmus, refers to its red eye and the White-shouldered Antbird’s name, Myrmeciza. melanoceps, means black-headed.
We describe and name many birds by their colors, but birds, having better
vision than us, can see not only the visible spectrum of colors but also UV light. Over 90% of birds examined reflect UV from their feathers and probably give birds a much different view of each other than we have. Male Blue Tits raise a UV reflective crown patch during courtship and the Blue Grosbeaks (Passerina caerulea )with the most UV reflection in their blue feathers are the most successful breeders. The black bibs of male House Sparrows indicate their level of dominance and the amount of spotting on a female Barn Owl’s breast indicates her parasite load to a potential mate.
“When nature made the bluebird she wished to propitiate both the sky and
the earth, so she gave him the color of the one on his back and the hue of the
other on his breast.” ~John Burroughs