Hummingbirds are known for their iridescent plumage that shimmers in the sunlight. Their feathers can display a spectacular array of colors, from fiery reds and oranges to deep blues and greens. But do these dazzling hues actually serve a purpose for the birds? Here we explore some of the leading theories about what different hummingbird colors mean and why they developed.
Identification
One of the most straightforward functions of hummingbird colors is for identification. There are over 300 different species of hummingbirds, and the colors and patterns of their plumage help distinguish between them. For example, an Anna’s Hummingbird can be identified by its bright green head and rose-pink gorget (throat patch), while a Ruby-throated Hummingbird has metallic green upperparts and a distinctive ruby red throat.
Like many birds, male and female hummingbirds often display different plumage colors, making it easier to differentiate between the sexes. Males tend to be more vibrantly colored, a trait believed to have evolved through sexual selection as a way to attract mates.
Camouflage
While hummingbird colors are often flashy, they can also serve as camouflage. Many species have plumage that blends in with their natural environment, providing concealment from predators and prey. For example, the Speckled Hummingbird has green upperparts speckled with white that resemble dappled sunlight filtering through foliage. Other hummingbirds have underparts lined with white streaks and spots, breaking up their silhouette against the sky.
Some hummingbirds even have changeable “iridescent” feathers that appear to shift in color depending on viewing angle. This allows their plumage to mimic the shimmer of leaves and blend into vegetation.
Communication
In addition to mate attraction, hummingbird colors are thought to play a role in communication. Bright gorgets and crests are frequently used in aggressive displays between males defending feeding territories. Certain hummingbird species also perform elaborate courtship rituals that involve flashing their vibrant plumage at potential mates.
Research has shown that the ultraviolet wavelengths reflected by some hummingbird feathers are visible to the birds but not humans. This ability to perceive UV “colors” beyond the human visual spectrum likely allows for additional nuanced communication.
Thermoregulation
Due to their tiny size, hummingbirds have a hard time retaining body heat. Some scientists believe that dark plumage colors help absorb radiant heat from the sun, allowing hummingbirds to maintain their high metabolisms even in cool conditions. Melanin pigments in black, brown, and dark iridescent feathers potentially help regulate temperature.
In support of this theory, many high altitude species that experience cold temperatures have predominantly dark plumage. The black coloration may serve a thermoregulatory role.
Antioxidants
Carotenoid pigments are responsible for many bright reddish and orangey hummingbird colors. Ingested through the diet, carotenoids are potent antioxidants that can boost immune function and neutralize free radicals. The vibrant carotenoid-based colors communicate a bird’s good health and nutrition to potential mates.
The peculiar diet of hummingbirds, which consists mainly of nectar and tree sap, is surprisingly low in carotenoid content. However, certain species seek out carotenoid-rich food sources like small insects to obtain sufficient antioxidant levels.
Light Interference
Structural coloration is responsible for most hummingbird iridescence. Tiny air bubbles and melanin granules in the feathers cause light waves to interfere and bounce off at certain wavelengths, producing shimmering metallic hues.
Adjusting the angle of incident light changes what wavelengths are reflected, accounting for the colorful shifting patterns. The flexibility of these built-in “light filters” allows hummingbirds to display a myriad of different colors from the same set of feathers.
Meanings of Specific Colors
Now that we’ve discussed some general mechanisms behind hummingbird coloration, let’s examine what some of the most common plumage colors typically signify:
Red
– Aggression and territorial displays in males
– Signals health and vigor
– Attracts mates
Orange
– Also used in competitive male displays
– Indicates fitness and nutritional status
Yellow
– Visual attraction for pollinators to flowers
– Used as “flash signals” in some species to attract mates
Green
– Camouflage and mimicry in vegetated areas
– Less aggressive displays than red/orange
Blue
– Rare and structurally-produced color in hummingbirds
– More research needed, but likely used for display
Violet/Purple
– Limited occurrence in a few species
– Suggested as indicator of genetic fitness
Black
– Thermoregulation and heat absorption
– Signals dominance in some species
White
– Camouflage and disruptive feather markings
– Frequently used as bold tail banding in maneuvers
Iridescence
– Flexible structural coloration for communication
– Dynamic shifts with angle mimic nearby surfaces
Geographic Variation
Interestingly, the colors and patterns of the same hummingbird species can vary across different geographic areas. This phenomenon, known as geographical polymorphism, suggests an influence of local environmental conditions.
For example, Allen’s Hummingbird males are reddish orange from the Pacific Northwest to Southern California. But in the Rocky Mountains and Mexico, Allen’s males are much more brightly colored with more intense orange hues. This variation implies an adaptive response to different settings.
In areas where food sources yield higher carotenoid levels, the males may be able to produce richer, more vibrant colors. Brighter males may have greater mating success in that particular habitat.
Juvenile Plumage
Young hummingbirds display different plumage colors than adults, likely for camouflage. Juveniles tend to be streaked and spotted in neutral browns and grays that resemble tree bark and faded vegetation. This provides crucial concealment while the vulnerable fledglings learn to forage.
As the birds mature, their adult colors start to emerge. Males also may go through transitional “subadult” plumages as their dazzling ornamental feathers develop.
Molting and Color Change
Hummingbirds undergo an annual molt where old worn feathers are replaced. Prior to molting, carotenoid pigments are withdrawn from the feathers and stored internally. Then vibrant new feathers quickly grow in.
The timing and progression of molt allows for seasonal color changes. Ruby-throated Hummingbird males transition from dull green in winter to fiery reddish-pink for the breeding season.
Some hummingbirds also have multiple distinctive plumages throughout the year, alternating between vivid breeding colors and cryptic non-breeding camouflage.
Summary of Hummingbird Color Meanings
| Color | Likely Meaning and Purpose |
|---|---|
| Red | Aggression, territory defense, mate attraction |
| Orange | Dominance signaling, nutritional health |
| Yellow | Pollinator attraction, visual signaling |
| Green | Camouflage and background matching |
| Blue | Status signaling and mate display |
| Violet/Purple | Potential indicator of fitness |
| Black | Heat absorption, dominance displays |
| White | Camouflage disruption, flashy maneuvers |
| Iridescence | Communication flexibility and signaling |
Conclusion
In summary, hummingbird colors have a range of functions from camouflage, communication and mate attraction to thermoregulation. Structural iridescence allows for dynamic and flexible signaling controlled by feather structure and angle of light. Carotenoid pigments indicate nutrition and health while melanins help absorb heat.
Geographic variation demonstrates local adaptation, with males in certain areas developing brighter, more dominant coloring. Molting enables seasonal shifts like flashy breeding plumage. Hummingbird colors are multifactorial, with many possible overlapping purposes from identification to dominance and display.
