Male Rufous Hummingbirds have beautiful, iridescent plumage that appears coppery red in bright light. Their coloration can range from an orange-red to a rusty, coppery hue depending on the angle of light. The vibrant, shimmering colors are a way for the males to attract females during mating season. Understanding the factors that influence their color and seeing how it can vary provides insight into these tiny, fascinating birds.
Plumage
The coloring of male Rufous Hummingbirds comes from specialized feathers called gorgets located on their throat and crown. Unlike typical feathers, gorgets have a unique structure that allows them to reflect light. They contain stacked melanin rodlets and air pockets that cause incoming light waves to split and reflect off one another, creating iridescence. Adjusting the angle of the feathers changes the paths of the light waves, which shifts the resulting color that is seen. This ability to manipulate their gorget feathers allows males to signal females with colorful, shimmering displays during courtship.
Molting
In addition to manipulating their existing feathers, the color of male Rufous Hummingbirds changes with the molting cycle. Molting is the process where old feathers are replaced with new ones. It occurs at least once a year, usually in late summer after mating season ends. When the males molt their gorget feathers, the new feathers have a brighter, more vibrant color. This readiness of fresh plumage prepares them for the next breeding season. The more intense hues help attract females and intimidate competing males. So a male Rufous Hummingbird’s gorget will be its most brilliant right after molting and then fade over time before the next molt.
Age
Younger male Rufous Hummingbirds, in their first year, have gorgets that are distinctly duller than older males. Their feathers tend to be more brownish and lack the fiery, coppery tones of mature adults. The subdued color is similar to female plumage. As the young males grow and go through their first molt, their gorget feathers will gain more color. Older males tend to have the brightest, more vivid plumage. So age is a factor in the intensity of coloration displayed.
Geographic Location
Interestingly, the color of male Rufous Hummingbirds also varies across their habitat range. Those found farther north tend to be brighter and more fiery orange-red. In the southern extent of their range, the males have more muted plumage in bronze-rusty hues. The reason for this geographical difference is not definitively known but may be related to environment, temperature, diet, and evolutionary adaptations. Northern, brighter males may stand out more against cooler green forests while southern males blend into drier, brown vegetation.
Location | Male Color Description |
---|---|
Pacific Northwest | Vibrant orange-red |
Southwestern U.S. | Duller rust-bronze |
Diet
The availability of food resources also impacts the color of male Rufous Hummingbirds. Carotenoid pigments obtained from their diet of tree sap, nectar, and small insects are responsible for the red-orange hues. Carotenoids are antioxidants that must be continually replenished through feeding. Males that have greater access to carotenoid-rich foods exhibit brighter plumage. In poorer environments, males will be paler and duller. So the quality of their habitat directly affects the intensity of their color.
Lighting Conditions
The inherent iridescent nature of Rufous Hummingbird gorget feathers means their color strongly depends on lighting conditions. Direct sunlight striking the feathers at the optimal angle will result in the most vivid, intense color display. In contrast, diffuse light, shade, or cloudy conditions all make the gorget appear dull. Additionally, since iridescence is caused by layered structures, the amount of light reflected also determines brightness. Low light results in a more subdued look while bright light enhances the gleaming color. So the same male can look strikingly different based on the lighting in its environment at the time.
Behavioral Factors
Not only do physical and environmental factors affect a male’s color but behavioral ones as well. During courtship displays, male Rufous Hummingbirds will orient themselves toward the sun to achieve maximum iridescence in order to impress females. Additionally, they puff up their gorget feathers to expose more of the color to potential mates. Both actions demonstrate that the birds can intentionally control their appearance to appeal to females through beautiful displays. The fleeting nature of these shows means color alone does not define an individual male as much as his behavior.
Individual Variation
There is natural individual variation in the coloring of male Rufous Hummingbirds, much like differences in human hair and eye color. While genetics play a key role, the degree of red or orange comes down to minute structural differences in the gorget feathers of each bird. The thickness and precise stacking of melanin, air bubbles, and keratin all affect light scattering and the resulting color produced. Diet, health, age, and molting impact these structures as well. Older males tend to have more strongly colored feathers but that is not always a given, as some simply have less robust pigmentation. So there can be significant color variability between males regardless of other factors.
Measuring Color
Ornithologists use specialized spectrometric equipment to accurately measure and quantify the colors of bird plumage. By shining calibrated light beams on feathers and analyzing the wavelengths reflected back, they can assign numerical values to colors along avian visual, UV, and human-visible spectrums. Doing this for Rufous Hummingbird gorgets allows precise color comparisons between individuals as well as calculating averages for groups across different regions. The data indicates northern birds reflect longer, redder wavelengths while southern birds have shorter, oranger wavelengths. But the range of colors along the spectrum measured demonstrates individual variation as well.
Example Spectrometry Data
Individual | Color Wavelength |
---|---|
Male A | 620 nm |
Male B | 640 nm |
Male C | 580 nm |
Conclusion
In summary, many different factors contribute to the coloration of male Rufous Hummingbirds. Their iridescent gorget feathers can display a range of bright orange and red hues depending on angle and light. Age, molting, diet, geography, behavior, and individual variation all play a role as well. Measuring the spectral wavelengths scientifically demonstrates the diversity of color these tiny birds can achieve. While breeding condition males tend toward more fiery plumage, no two are exactly alike in their vibrant appearance. The intricacies of their coloration reveal the beauty and wonder of these energetic, shimmering creatures. Paying attention to the variations can give you new appreciation for Rufous Hummingbirds.