The gorget is a flashy, iridescent bib of feathers on the throat of male Anna’s hummingbirds (Calypte anna). It is one of the most striking features of this tiny bird, ranging in color from rose-pink to magenta depending on the viewing angle. The gorget plays an important role in mating displays and territorial defense for the Anna’s hummingbird. In this article, we will explore what exactly the gorget is, its function, how it develops, and some interesting facts about this unique plumage.
What is a gorget?
A gorget refers to a patch of distinctive feathers, skin, or fur around the throat. The term comes from the Middle French word meaning “throat armor”, originally referring to a piece of armor that protected the neck.
In birds, gorgets typically refer to bib-like patches of iridescent feathers on the throats of hummingbirds and some related species. The Anna’s hummingbird has one of the most vibrant and conspicuous gorgets among North American hummingbirds.
Anna’s Hummingbird Gorget
The male Anna’s hummingbird has an iridescent gorget that covers the entire throat and chin. It is bordered by a thin white stripe along the lower edge.
When relaxed, the gorget feathers lay flat and overlap, appearing grayish or dark rose in color. But when the bird displays, the gorget feathers are fanned out, revealing their full iridescent glory.
The Anna’s hummingbird’s gorget flashes brilliant magenta and rose-pink, with some emerald green fringes. The exact hue depends on the viewing angle. This iridescence is created by tiny nanostructures in the feathers that refract light.
Functions of the Gorget
The Anna’s hummingbird uses its dazzling gorget in the following ways:
Courtship Displays
Male Anna’s hummingbirds perform dramatic courtship displays to attract females. These displays involve flying in U-shaped or J-shaped dives up to 100 feet in the air. At the bottom of the dive, the male will flare out his tail feathers and spread his gorget wide like a fan.
The iridescent gorget catches the female’s attention. The wider and more vibrant the gorget appears, the more desirable the male is. After mating, the female will use the male’s gorget brightness to select the most attractive male as her mate.
Territorial Displays
Adult male Anna’s hummingbirds are highly territorial. They defend feeding areas known as territories against intruders.
When an intruder approaches, the male performs an aggressive display. This involves hovering in place and orienting his body so the iridescent gorget faces the intruder. The bright gorget acts as a threat signal to scare away the intruder.
Species Recognition
The Anna’s hummingbird’s distinct gorget sets it apart from other similar hummingbird species at a glance. This helps with species recognition between male hummingbirds as they establish breeding territories.
Females may also use the male’s species-specific gorget pattern to recognize appropriate mates of their own kind.
Gorget Development
Anna’s hummingbird gorgets change dramatically through the bird’s life stages:
Juveniles
Both male and female Anna’s hummingbird juveniles lack a gorget. Their throats are gray-white.
Females
Adult females retain the grayish throat plumage. They may develop a few iridescent throat feathers, but lack a complete gorget.
Males
Adult males molt into their full gorget plumage when they are 1-2 years old.
Testosterone drives gorget development. Castrated males fail to develop a gorget.
The iridescent feathers regrow each time the bird molts. Older males tend to have larger, more brilliant gorgets.
Interesting Gorget Facts
Size
Larger gorgets are more attractive to females. In one study, males with gorgets 20% larger than average sired nearly all the offspring.
The Anna’s hummingbird’s gorget measures about 1 inch long. Other hummingbirds have proportionally larger or smaller gorgets.
Iridescence
The Anna’s hummingbird gorget’s iridescence does not come from pigments, but from nanostructures in the feathers. These include:
- Thin film layers
- Air bubbles
- Melanin granules
Combined, these structures refract incoming light rays to produce the colorful, shimmery gorget effect.
Color Range
The Anna’s hummingbird’s gorget flashes different hues ranging from magenta to rose-pink as the viewing angle changes. This is caused by the thin film layers in the feathers.
At near perpendicular angles, shorter wavelengths like violet and blue are reflected, making the gorget appear magenta. At shallow angles, longer orange and red wavelengths predominate, resulting in a pinker hue.
Glow
The male Anna’s hummingbird’s gorget may glow weakly in dim light. This effect, called photoluminescence, is caused by the feathers’ nanostructures capturing and re-emitting energy from ambient ultraviolet light.
Comparison with Other Hummingbirds
Here is how the male Anna’s hummingbird’s gorget compares to other western North American hummingbirds:
| Species | Gorget Size | Color |
|---|---|---|
| Anna’s Hummingbird | Small | Magenta to pink |
| Costa’s Hummingbird | Very small | Purple |
| Rufous Hummingbird | Medium | Orange |
| Allen’s Hummingbird | Large | Orange-red |
| Calliope Hummingbird | Speckled | Magenta-red |
As the table shows, the Anna’s hummingbird has a small but vibrantly colored gorget compared to related species. The Allen’s hummingbird has the largest and showiest gorget in its range.
Conclusion
The flashy gorget is an essential feature for male Anna’s hummingbirds. This iridescent bib plays key roles in mating displays, territorial defense, and species recognition. Its color, size, and brilliance are critical indicators of male quality for female mate selection. The Anna’s hummingbird’s distinctive gorget sets it apart from other western hummingbird species. This iconic patch of colorful feathers has captivated researchers and bird enthusiasts alike as they unravel its many functions and intriguing underlying structural mechanisms.
