Hummingbirds are among the most colorful creatures because of the feathers that they wear. This is mostly attributable to a particular mechanism.
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There is a far wider range of hues represented in the plumage of birds than was previously understood. This is shown by research conducted on the feathers of over one hundred different species of hummingbirds. According to this, the majority of the colors of these birds are not, as is typically the case, due to special color pigments such as melanin, but rather to light effects that are primarily based on the fine structure of the plumage. This is in contrast to the common belief that special color pigments such as melanin are responsible for the majority of the colors of birds. This results in the iridescent coloration that is characteristic of many Trochilidae species of hummingbirds, the intensity of which also varies on the angle at which the light is incident.
According to research published in Communications Biology by a group of researchers lead by Richard Prum from Yale University, colors serve a variety of purposes in animals, ranging from thermoregulation to communication. Because of this, birds are among the creatures that have the broadest range of hue. This is possibly partly owing to the fact that their retina includes four different kinds of cone cells, which is one more type than the cone cells found in human retinas: They contain a set of photoreceptors that are sensitive to violet and ultraviolet light in addition to the cones that are sensitive to light of short, medium, and long wavelengths.
After conducting research on 111 bird species belonging to a variety of families and publishing his findings in the journal Behavioral Ecology in 2011, Prum has previously identified the color spectrum of bird feathers. His team has now looked at the feathers of 114 different species of hummingbirds belonging to 68 different genera. This accounts for around one third of the species that belong to this family of birds, which is exclusive to the Americas.
"Hummingbirds increase the known spectrum of bird feathers and encompass color ranges that were previously unreported," the team says, pointing out in particular strong greens and blues. "Hummingbirds expand the known spectrum of bird feathers." In all, the color spectrum of the hummingbirds that were analyzed encompassed around 85 percent of the whole range that is known to exist in birds.
This is not so much because of the colors that are created by pigments like melanin, but rather because of the colors that are referred to as structural colors. These are brought by by interference, which may be defined as the superimposition of several light waves, and are the result of the interplay of a number of different components inside the birds. These include the intricate structure of the feathers and the several layers of unique organelles that are generated in pigment cells and are referred to as melanosomes. Other examples include the exquisite structure of the interconnecting feathers.
The team highlights that this specific process for coloring is the most adaptable one and that it is especially sophisticated in hummingbirds. It goes on to say that "not only are hummingbirds a very colorful family, but they also comprise nine of the most colorful bird species known," which is a really interesting fact. Specifically included in this category is the Boissonneaua jardini, sometimes known as the hyacinth hummingbird, which is native to South America.
Hummingbirds, in general, have coloration that is most prominent on their heads and throats. This is because these areas are highly crucial for the birds' ability to communicate with one another and because they shimmer beautifully when the bird's head is turned towards a spectator.
The researchers also explain why the blaze of color is so prominent in hummingbirds in particular. According to their findings, this is tied to a variety of factors, including the age of the bird family and the number of species that make up the family. It argues that hummingbirds are superior in all of these categories. Over the last 22 million years, there has been a remarkable expansion in the number of hummingbird species, which now numbers 336. Because of selection, the range of hues has gotten noticeably more distinct throughout the course of this period.