Hummingbirds are known for their beautiful, iridescent plumage. One distinctive feature many hummingbird species have are gorgets – colorful, often metallic feathers around the throat. Gorgets come in a stunning array of colors and patterns, making them an eye-catching aspect of hummingbird anatomy. But what exactly are gorgets, and what purpose do they serve for hummingbirds? Here we’ll explore the details of hummingbird gorgets and what they can tell us about these captivating birds.
What is a Gorget?
A gorget refers to a patch of distinctive feathers around the throat. The term comes from a piece of armor called a gorget that was worn around the neck and throat. Similarly, the colorful gorget feathers protect and encircle a hummingbird’s throat. Gorgets are made up of highly specialized feathers called plumulaceous feathers that contain plate-like structures that refract light. This leads to the striking iridescent, shimmery quality of gorget feathers.
While many birds have some ornamental throat feathers, hummingbird gorgets are unique in their vibrant colors and defined shape. The shape of the gorget varies by species – some form a neat collar while others have more diffuse patches of feathers. The color also varies dramatically, spanning all colors of the rainbow. Red, fuschia, blue, green, and purple are just some of the dazzling colors that occur in hummingbird gorgets.
Some common gorget patterns include:
– Solid band – A uniform patch, like the ruby red gorget of a Ruby-throated Hummingbird
– Speckled – Tiny dots, like the dotted pattern on a Berylline Hummingbird’s throat
– Stripes – Distinct lines, like the striped gorget of a White-necked Jacobin
– Gradient – Gradual color change, seen on the Anna’s Hummingbird as it shifts from rose pink to bright iridescent purple
So in summary, a gorget refers to a specialized, iridescent patch of feathers around a hummingbird’s throat that serves an ornamental purpose. The shape, size, color and patterning create endless variations between species.
Functions
Hummingbird gorgets serve a few key functions:
Identification
The unique gorget of each hummingbird species allows for identification. Just a quick look at the throat can help observers distinguish between say, an Orange-throated Sunangel and a Black-throated Brilliant. Gorgets are like colorful name tags that help separate the over 300 different hummingbird species. Even young fledglings have identifiable gorget colors, meaning the gorget aids in parent-offspring recognition as well.
Attracting a Mate
Gorgets play an important role in courtship and mating. Their bright colors serve to attract potential mates. Studies have shown that female hummingbirds tend to prefer males with the brightest gorget feathers, as this indicates health and vigor. The striking gorgets are considered a sexually selected characteristic, meaning evolution has led to embellished gorgets as it enhances mating success.
Communication
In some species, the gorget feathers are used to communicate with other birds. Male hummingbirds can puff up their gorgets when defending a territory or during high-speed dive displays. Females may flatten their gorgets to signal submission to a male. The flexibility of the gorget feathers allows for non-vocal communication. Additionally, as the feathers shift in the light, the color patterns change, which can transmit information. Gorget flashing likely conveys messages that are key to mating rituals and social interactions.
Defense
The tough, tightly packed feathers provide protection for the vulnerable throat area. Predators like birds of prey often target the neck, so the shield-like gorget offers an extra layer of safety. When threatened, some hummingbirds can expand their gorgets to appear larger and more intimidating. The eye-catching flash of the gorget may also momentarily startle a predator long enough for the tiny hummingbird to escape.
Thermoregulation
There is evidence that gorgets may aid in temperature regulation. The dense feathers around the throat likely help prevent heat loss. During cold periods, hummingbirds can fluff up their gorgets for additional insulation around this vital area.
Colors
What accounts for the incredible range of gorget colors in hummingbirds? The secret lies in the structure of their feathers.
Iridescence
Most gorget colors are iridescent, meaning they appear to change hue with viewing angle. This shimmering quality is produced by light refracting off intricate nanoscale structures in the feathers. The shapes vary slightly between species, resulting in different colors.
| Species | Gorget Color |
|---|---|
| Ruby-throated Hummingbird | Ruby red |
| Anna’s Hummingbird | Rose pink to purple |
| Costa’s Hummingbird | Violet-purple |
| Rufous Hummingbird | Rufous orange |
Pigmentation
In some cases, pigments also contribute to gorget color. Carotenoid pigments produce some of the red hues. Melanin creates dark spots or banding effects. By combining structural colors and pigments, hummingbirds can achieve a whole spectrum of gorget shades.
UV Reflectance
Recent studies have shown that hummingbird gorgets reflect ultraviolet light. This UV reflectance is invisible to human eyes but visible to birds. So a dull grey gorget may burst with UV signals that are meaningful to other hummingbirds. This added UV dimension is suspected to play a role in mate selection and territorial interactions.
Size and Shape
There is significant variation in gorget size and shape between the different hummingbird species:
| Species | Gorget Shape | Total Length | Gorget Size |
|---|---|---|---|
| Anna’s Hummingbird | Oval | 3.5 – 4 inches | Half neck circumference |
| Costa’s Hummingbird | Round | 3.5 – 4 inches | Full neck circumference |
| Rufous Hummingbird | Speckled band | 2.8 – 3.5 inches | Third of neck circumference |
| Ruby-throated Hummingbird | Pointed oval | 2.8 – 3.5 inches | Half neck circumference |
In terms of overall size, larger hummingbird species tend to have proportionally larger gorgets. Within a species, males typically have larger, flashier gorgets than females.
The shape also varies, with some having sharply delineated edges and others having a diffuse transition into the breast feathers. Circular gorgets that fully encircle the throat are the most common. Species with small patches or speckled patterns have smaller gorgets.
Molting
Hummingbirds molt and replace their gorget feathers at least once a year after breeding season. The old gorget feathers are shed and new ones grow in.
Young fledglings don’t initially have bright gorget colors. Dull juvenile gorget feathers are replaced with adult plumage after the first molt. For young males, the first vibrant gorget helps attract mates during the next breeding season.
Molting is energetically expensive given the specialized structure of gorget feathers. Hummingbirds have adapted to timing their molt to seasons when food is plentiful. Adult males also lose their gorgets immediately after mating. This is presumed to allocate more energy towards survival and migration.
The timing of gorget molting varies by species and location:
| Species | Molting Period |
|---|---|
| Ruby-throated Hummingbird | January-March |
| Black-chinned Hummingbird | July-September |
| Anna’s Hummingbird | July-December |
| Costa’s Hummingbird | February-April |
Behavioral Changes
Hummingbirds can rapidly manipulate their gorget feathers to create dynamic displays:
Puffing
When agitated or excited, hummingbirds can puff up their gorget feathers to appear larger and more impressive. This behavior is seen during conflicts between males over territory or food sources. Females may also puff up their gorgets when initially interacting with a potential mate.
Flattening
The gorget can be flattened against the body to appear smaller and more submissive. Young birds tend to flatten their gorgets when approaching adult birds. Females may also flatten their gorget as a signal of acquiescence to a dominant male.
Fanning
Rapid fanning or flashing of the gorget creates a dramatic pulsating effect. This is seen during acrobatic dive displays by males trying to impress potential mates. The constant ripple of color likely helps attract attention.
Positioning
By adjusting the angle and position of the gorget feathers, hummingbirds can alter their appearance. Tilting the gorget to display the throat is used to issue challenges and signal aggression between males. Facing the gorget away can signal submission or non-aggression.
Evolutionary Origins
The evolutionary origins of hummingbird gorgets are still debated. Here are two leading theories:
Sensory Bias
This theory proposes that female hummingbirds developed an innate preference for bright, shimmering colors that reminded them of flowers. Males then evolved elaborate gorgets through sexual selection to capitalize on this preexisting female sensory bias.
Species Recognition
Others argue gorgets arose primarily for species recognition rather than attraction. As hummingbirds diversified, distinctive gorget colors enabled birds to quickly identify their own species. This facilitated correct mating choices and reduced hybridization between emerging species.
In both cases, once female preference led to spectacular male gorgets, this kicked off further amplification through mate choice and competition between males. This accounts for the incredible diversity and ornamentation seen in modern hummingbird gorgets.
Regional Differences
There are some noteworthy geographical trends in hummingbird gorgets:
Tropical South America
This region has the highest hummingbird diversity and the most vibrant gorget colors, like the neon purple gorget of the Andean Emerald. Competition for mates and food sources may drive stronger selection for fancy gorgets.
North America
Hummingbirds in North America tend to have somewhat drabber gorgets in reddish or grey hues. Exceptions include the iridescent purple gorget of the Costa’s Hummingbird.
Island Species
Island species like the Bee Hummingbird found only in Cuba display less flashy gorgets. With fewer competing species on islands, garish gorgets may be less crucial for attracting mates.
So in summary, hummingbird gorget evolution seems closely tied to species diversity and competition pressure, leading to more elaborate designs in highly diverse hummingbird assemblages.
Pollution Effects
Air pollution can diminish the vibrant colors of hummingbird gorgets. Studies have shown that exposure to a common urban pollutant called ozone results in faded, tattered gorget feathers.
This effect is believed to result from the oxidative stress caused by ozone exposure degrading the organic nanostructures that produce iridescence. Unfortunately, this loss of color could potentially reduce mating success.
Providing hummingbirds with clean habitats away from heavy pollution may help preserve the integrity of their magical gorget feathers.
Conclusion
Hummingbird gorgets comprise some of the most striking plumage in the avian world. These specialized throat feathers play a key role in mating rituals, communication, and identification thanks to their varied shape, size and iridescent coloration. The complex structure of the feathers allows for shimmering optical effects that likely captivated hummingbird evolution through sexual selection. While many details remain to be uncovered about their formation and function, it is clear that gorgets provide a flashy display that captures the allure of hummingbirds. When we admire the sparkle at a hummingbird’s throat, we are witnessing an elegant evolutionary outcome etched in delicate feathers.
