Yes, there are over 300 different species of hummingbirds that come in a spectacular array of colors. Hummingbirds are found naturally only in the Americas, where they have adapted to a wide range of environments and developed unique plumage colors. Their vibrant, metallic colors are a result of specialized feather structure rather than pigment. When light hits their feathers, the color that is reflected depends on the angle. By shifting position, hummingbirds can display different hues. Let’s take a closer look at some of the most strikingly colored hummingbirds and what accounts for their beautiful feathers.
What gives hummingbirds their bright, metallic colors?
Unlike many other brightly colored birds, hummingbirds get their dazzling iridescent colors from structural coloration rather than pigments. Their feathers contain nanoscale structures that interfere with light waves to reflect certain colors. When viewed from different angles, the colors seem to shift and change. Here are some of the special adaptations that allow for structural color in hummingbirds:
Melanin granules
Melanin is the same pigment that gives human skin and hair its color. But in hummingbirds, tiny melanin granules are layered on top of the barbules of the feathers. This provides a dark background that lets the metallic colors stand out more.
Keratin overlayers
The feather barbules also contain flattened keratin cells layered on top of one another. These transparent keratin layers have slightly different thicknesses that reflect different wavelengths of light.
Air pockets
Tiny air bubbles are trapped between the keratin layers. These air pockets amplify certain light waves through interference.
By precisely controlling the thickness of keratin layers and the size and distribution of melanin granules and air pockets, hummingbirds can create specialized feather structures that reflect specific colors.
Common hummingbird colors and what causes them
Here are some of the most common hummingbird colors and how their feather structure produces them:
Ruby red
The ruby throats of ruby-throated hummingbirds and the crimson star on Anna’s hummingbirds are produced by very thin keratin overlayers. This allows longer wavelengths of red light to be reflected.
Emerald green
Green hummingbirds like the green-crowned brilliant get their jewel-like color from slightly thicker keratin layers that reflect green light wavelengths. The width between layers creates constructive interference of green.
Sapphire blue
Medium thickness keratin leads to constructive interference of blue light waves in birds like the sapphire-spangled emerald.
Golden yellow
To produce yellow colors like that of the golden-crowned emerald, the keratin layers are arranged to reflect longer yellow wavelengths.
What other factors influence hummingbird colors?
While feather structure is the main determinant of color, other factors can also affect the hue:
Iridescence
The iridescent quality of hummingbird feathers causes drastic color shifts when viewed from different angles. This is caused by the interference of light waves bouncing off the complex feather layers.
Direction of light
Hummingbirds can appear to change color as they move because of the directionality of the reflected light from their feathers. The same feathers can produce different colors depending on viewing angle.
Absorption of light
Certain wavelengths of light may be absorbed by the melanin pigment rather than reflected, which can influence the resulting color. More melanin filters out more light.
Combination of colors
Some vibrant colors like violet come from a combination of certain keratin layer widths with melanin filters that produce a blend of reflected hues.
Do males and females have different colors?
In most hummingbird species, the males have the more vibrant, metallic plumage. Females tend to be less brightly colored with more muted greens, grays, and whites in their plumage. Here are some reasons for this sexual dichotomy in color:
Camouflage
Duller female plumage provides more camouflage while incubating eggs and caring for young. Bright males can be more conspicuous targets.
Attracting mates
Male hummingbirds use their brilliant colors to attract female attention and outcompete other males. Their flashy feathers signal fitness.
Testosterone
Higher testosterone levels in male hummingbirds may drive the development of more flamboyant structural coloration.
Genetic differences
Sex-linked genetic differences likely underlie many of the color variations between males and females. More research is needed.
How do hummingbird colors vary geographically?
Hummingbirds’ vibrant colors are shaped in part by their environment. Here are some geographic trends:
Forest light conditions
Low light conditions in dense forests favor iridescent plumage that flashes brightly as the birds move between sun flecks. Hummingbirds of the rainforest have very vibrant colors.
Altitude adaptations
High altitude species like the Andean hillstar have more melanin pigmentation. This absorbs light and heat more efficiently in cold mountainous areas.
Mimicry
In some cases, hummingbirds have evolved similar colors to other species in their habitat. For example, the bee hummingbird resembles a bumblebee.
Pollinator preferences
Flower pollinator coevolution may drive localized preferences for certain colors of hummingbirds. Hummingbirds and flowers adapt together.
Sexual selection
Female color preferences have likely contributed to the evolution of bright male plumage in some species. This can vary by region and habitat.
Some of the most vibrantly colored hummingbirds include:
| Species | Colors | Range |
|---|---|---|
| Anna’s Hummingbird | Ruby red crown and throat, emerald green back | Western North America |
| Ruby-throated Hummingbird | Ruby red throat, emerald green back | Eastern North America |
| Costa’s Hummingbird | Violet-purple crown, blue throat, green back | Southwestern North America |
| Violet-tailed Sylph | Violet crown and tail, green belly | Andes Mountains |
| Violet-headed Hummingbird | Violet crown, white underparts | Central America |
What causes some hummingbirds to have little or no color?
While vibrant colors are common in hummingbird plumage, some species are quite dull by comparison. Here are reasons some hummingbirds lack flashy colors:
Camouflage
Those that inhabit darker forests may have subdued blacks, grays, and browns in their plumage to blend into the environment. Camouflage protects against predators.
Less sexual selection
In species where males do not need flashy displays to attract mates, lack of sexual selection can lead to reduced color over time.
Genetic differences
Natural genetic variation means some species inherit less capacity for specialized structural colors.
Younger birds
Juvenile and female hummingbirds are less colorful until they molt and acquire their adult plumage. Young birds have poorer feather structure.
Dietary deficiencies
Malnutrition while growing new feathers can degrade color. Key nutrients enhance color.
Major factors influencing hummingbird colors:
| Factor | Effect on Color |
|---|---|
| Feather structure | Main determinant of metallic iridescent colors |
| Melanin granules | Absorbs certain wavelengths to produce vibrant colors against dark backgrounds |
| Keratin overlayers | Thin layers reflect red light, thicker layers green then blue |
| Air pockets | Amplify light interference effects |
| Iridescence | Allows color to shift dramatically with viewing angle |
| Direction of light | Determines which wavelengths are reflected based on angle of incidence |
| Absorption | Melanin absorbs certain wavelengths, removing those colors |
| Combination | Mix of structural effects can blend multiple hues |
| Environment | Adaptations to habitat such as rainforest light and altitude affect color over time |
Conclusion
Hummingbirds dazzle with their stunning metallic colors produced by specialized feather structures. Tiny variations in melanin, keratin, and air layers create shimmering reds, greens, blues, and violets. Male birds tend to have the most vibrant colors for attracting mates in displays. Geographic adaptations lead rainforest species to have more iridescence, while high altitude birds develop more heat-absorbing melanin. Though some species are duller for camouflage, hummingbirds stand out as one of nature’s most radiant marvels. Their tiny bodies are bursting with spectral brilliance.
