The ruby-throated hummingbird (Archilochus colubris) is one of the most common and widely recognized hummingbird species in North America. As their name suggests, ruby-throated hummingbirds have brilliant, metallic red throats that catch the eye when they visit feeders and flowers. But what are the other colors that make up their distinctive plumage? Keep reading for a deep dive into the coloring and feather anatomy that gives ruby-throated hummingbirds their dazzling beauty.
Males vs Females
Like many bird species, male and female ruby-throated hummingbirds have slightly different plumage colors. Here is a quick overview:
Males
– Metallic red throats
– Iridescent green backs and heads
– Grayish-white undersides
– Black tails with white tips
Females
– White throats
– Green backs
– Grayish white undersides
– Black tails with white tips
The males sport the flashier, more colorful plumage overall. Their bright red throats are like vibrant, flags advertising to females and warning off competing males. Meanwhile the female’s white throat blends in with her underside, a more camouflaged look.
Feather Structure
To understand ruby-throat coloring, it helps to know a little bit about feather anatomy and how feather structure determines color.
There are two main types of feathers:
Contour feathers – These are the feathers that form the visible outer plumage on a bird. They have interlocking barbs and barbules that create a smooth surface.
Down feathers – These are found closer to the skin and lack the interlocking structures of contour feathers. They have more of a fluffy appearance. Their main role is insulation and warmth.
On a ruby-throat, the contour feathers of the throat, back, chest, and tail determine color. Within these feathers are structures called melanosomes. Melanosomes contain melanin pigments that produce black, brown, reddish-brown, and, when layered with other cell structures, iridescent colors.
The shape, density and layering of melanosomes affect what color the feather appears. By packing together rod-shaped melanosomes, ruby-throats can structurally produce the metallic red, iridescent feathers of the male’s throat.
Iridescent Coloration
Male ruby-throats have feathers that are iridescent. This means they appear to change color when viewed from different angles. This shimmering quality is produced by layers of melanin, air pockets, and keratin proteins in the feathers. As light hits them, different wavelengths are reflected back to the eye, creating a sense of moving, fluid color.
In bright light, the iridescent feathers appear metallic red or green. But in lower light conditions, the color is less intense. The effect evolved to allow hummingbirds to control the level of flashiness they exhibit. Males can turn up the iridescence to impress females and chase off competitors, or tone it down when camouflage is more important.
Melanin Distribution in Key Feather Groups
The various feather groups of a ruby-throated hummingbird contain melanin pigments in different concentrations and distributions. This melanin patterning leads to the distinctive colors in different parts of their bodies.
Throat feathers
As described above, the male’s throat feathers contain specialized rod-shaped melanosomes packed into layered structures. This creates the flashing metallic red iridescence. Females have less densely packed melanosomes in a flatter arrangement, leading to a plain white throat.
Crown and back feathers
Both sexes have iridescent emerald green feathers covering the crown and back. These feathers have similar melanosome properties as the male’s throat, creating a green color when light hits them. The effect is slightly less pronounced than the male’s throat.
Chest and belly feathers
Ruby-throats lack melanin almost entirely in their chest and belly feathers. This results in a pale grayish-white color on the underside. Without melanosomes to darken the feathers, the underlying white and buff hues are visible.
Tail feathers
Finally, ruby-throated hummingbird tails contain large amounts of eumelanin. This gives both sexes a mostly black tail. The outermost tail feathers have white tips though, adding a subtle highlight when the tail fans out in flight.
How Coloration Develops
Ruby-throated hummingbird chicks hatch with almost no feathers. Their coloring at this stage is defined by their pinkish-gray bare skin. After about a week, the chicks develop their juvenile plumage.
Juveniles of both sexes resemble the adult female. They have green upperparts, white-gray undersides, and the black tails with white tips. The males do have some scattered iridescent red feathers mixed into the throat though, beginning the development into their adult plumage.
After their first molt around one month old, young males gain increasing red color in their throat feathers. By about 10 months old, the males complete the full transition to the metallic red throat and brilliant green plumage. Females progress through molts but retain their more subdued white throat and back feathers.
Geographic Variation
The plumage of ruby-throated hummingbirds remains fairly consistent across their wide geographic breeding range in North America. Slight variations may occur though, typically in the brightness and saturation of the male’s red throat feathers.
Males found in the southern parts of the range may have especially vibrant throats. More northern breeders can look slightly duller in comparison. But the overall patterning and colors are alike throughout. No distinct subspecies of ruby-throat are currently recognized.
Examples in Photos
Ruby-throated hummingbirds offer so much to appreciate about specialized feather adaptations. Here are some photos highlighting key aspects of their stunning colors and patterning:
This male shows the metallic red throat and iridescent green back plumage.
The female ruby-throat has a white throat and gray-white underside feathers.
From this angle, you can see the black tail feathers with bold white tips.
Flying Displays
One of the best ways to appreciate ruby-throat hummingbird colors is by watching males perform flying displays. Watch how the colors shift and gleam as they rapidly dive and turn.
Here’s a great example flying display caught on video:
Conclusion
The ruby-throated hummingbird shows how feather structure, melanin distribution, and iridescence all work together to produce vivid plumage. Their metallic reds and greens seem almost too brilliant to be real. But they are just the product of adaptations that ensure males grab attention and help the species find mates and thrive. By understanding a little about feather anatomy and coloration mechanisms, we can better appreciate the dazzling details built into ruby-throated hummingbirds and other species. Their colors may be small, but they make a huge visual impact.