Hummingbirds are known for their ability to hover and fly backwards, which is unique among birds. This is made possible by their wings, which beat on average around 50 times per second. But if you look closely at a hummingbird’s wings, you may notice that they appear to be transparent in bright light. So do hummingbirds really have see-through wings?
The short answer is yes, hummingbird wings are partially transparent. However, the level of transparency depends on the angle you view them and how much light is passing through. When lit from behind or the side, the thin feather structure allows some light to shine through in certain areas. But the wings are not completely clear and still contain coloration and patterns.
Anatomy of hummingbird wings
To understand the partial transparency of hummingbird wings, it helps to look at their basic anatomy and composition:
Feathers
Hummingbird wing feathers are incredibly thin, narrow, and lightweight. This allows them to move their wings rapidly without causing drag. The feathers are made of beta-keratin like other bird feathers, but they have fewer interior structures. With fewer protein structures present, more light is able to pass through.
Bones
The “fingers” or bones in hummingbird wings are proportionally much longer than other birds. Their wings also contain fewer secondary flight feathers anchored to these bones. This further reduces the surface area and mass of the wings.
Muscles and skin
Hummingbird wing muscles and skin are stretched thinly across their wing bones. The wing membranes contain very little tissue overall, mostly just enough to attach the structures critical for flight. Again, the minimal material present enables more light to shine through.
So in essence, the composition and layout of tissues in hummingbird wings creates areas of partial transparency where light can pass between the feather shafts and through the thin skin. Next we’ll look at factors that influence the level of transparency.
Factors affecting the transparency
Angle of light
Hummingbird wings will appear more transparent when a bright light source, such as sunlight, is coming from behind or from the side of the wing at a suitable angle. If lit from the front or at too extreme of an angle, less light will pass through and they will look more opaque.
Light intensity
Bright sunlight allows for the most light passage, making the wings look very transparent in some spots. In low light conditions, the wings will generally look more solid and colorful.
Coloration
Some hummingbirds have wings with vivid iridescent colors, while others are more subtly patterned. Areas of pigmentation will block more light compared to unpigmented sections. So species with more bold and extensive coloration tend to have less wing transparency.
Molting
Hummingbirds molt and replace their wing feathers periodically. New growing feathers may be more susceptible to breakage, so they tend to have a more dense structure temporarily. This can reduce transparency until the feathers mature. Molting birds may also lack some color until new feathers grow in.
Age
Younger hummingbirds have fresher, newer plumage with optimal light passage. As birds age, their feathers become more worn and fray at the edges, reducing transparency.
So in summary, the most optimal conditions for seeing hummingbird wing transparency occur when sunlight strikes mature, minimally colored feathers at just the right angle. Next we’ll look at the purpose of this adaptation.
The purpose of transparency
Hummingbird wings did not evolve to be transparent. Rather, it is a byproduct of the thin feather and bone structure that enables their unique flight abilities. However, there are some potential benefits:
Reduced solar heating
Partial wing transparency may help prevent overheating from the sun. By allowing some light to pass through their wings, less solar energy is absorbed.
Camouflage
The ability to blend into the background may make hummingbirds less visible to predators when sitting still. Areas of thinner feather coverage could essentially create viewing “windows” to help them disappear against vegetation.
Intraspecies signaling
Colorful and iridescent wing patches are used for mating displays. Transparency may allow hummingbirds to flash these colors at each other while reducing visibility to predators. The flashing caused by wing flapping against the light likely also serves as a communication signal.
So in some ways, the transparency may provide secondary advantages. But the minimalist wing structure itself evolved mainly to enable sustained hovering and agile flight.
Differences between species
There are over 300 species of hummingbirds that exhibit varying degrees of wing transparency:
Ruby-throated Hummingbird
The Ruby-throated Hummingbird found in eastern North America has mostly green plumage with some red throat coloring on the males. Their wings show moderate transparency.
| Ruby-throated Hummingbird Transparency |
|---|
| Moderate transparency |
| Some clear areas against light |
| Females and juveniles more transparent |
Anna’s Hummingbird
Anna’s Hummingbirds on the west coast have extensive iridescent rose-pink coloring on their throats and crowns. Their wings tend to be less transparent due to the dense pigmentation.
| Anna’s Hummingbird Transparency |
|---|
| Low transparency |
| Pink and purple hues opaque |
| Small amount of translucence in feathers |
Costa’s Hummingbird
Costa’s Hummingbirds are found in the southwestern deserts. Their wings are mostly transparent with only tiny flecks of black, allowing them to nearly disappear when backlit.
| Costa’s Hummingbird Transparency |
|---|
| Very high transparency |
| Minimal dark pigmentation |
| Heavily backlit wings nearly invisible |
So in species with less extensive coloring, the wings tend to appear more see-through. But even among hummingbirds with vivid iridescence, parts of the wings will still transmit light.
Differences between male and female hummingbirds
In many hummingbird species, the males have colorful plumage for courtship displays. This often results in differences in wing transparency between males and females:
| Sex | Plumage | Transparency |
|---|---|---|
| Male | Iridescent colors on head, throat, and shoulders | Lower due to pigmentation |
| Female | Primarily green or grey plumage | Higher with less pigment present |
So male hummingbirds, with their bolder feather colors, tend to have less wing transparency compared to the more cryptically colored females. But even the flashier males still have some portions of the wings that show through when backlit. The degree of transparency depends on the specific species and the extent of the male’s colorful display feathers.
Do hummingbird wings function like insect wings?
Some people speculate that hummingbirds have transparent wings like insects. But despite some superficial similarities, the wing structure and function actually differs greatly between hummingbirds and insects:
Composition
Hummingbird wings are made of feathers, bone, skin, and muscle whereas insect wings are extensions of the exoskeleton. Insect wings are a thin double layer of cuticle surrounding hollow veins. They contain no bones or feathers.
Movement
Hummingbirds have jointed wings that rotate in a figure-eight pattern. Insects can only flap their wings up and down.
Aerodynamics
Hummingbirds create lift on both the downstroke and upstroke. Insects generate lift only on the downstroke and cannot fly backwards.
Transparency function
In insects, the transparency aids camouflage and communication. In hummingbirds, it mainly results from adaptations for rapid flight.
So while the wings of hummingbirds and insects may appear somewhat similar in bright light, they are very different anatomically and functionally. This limits the comparisons that can be made between them.
Conclusion
In conclusion, hummingbird wings are partially transparent due to their minimized feather, bone, and muscle structure. This enables them to beat their wings up to 50 times per second for hovering flight. While not completely clear, backlighting does allow some light passage through their thinly constructed wings. The degree of transparency depends on factors like molting stage, age, coloration, and lighting conditions. Transparency likely provides secondary benefits such as camouflage but primarily arises from evolutionary adaptations for sustained rapid flight, which differentiates them from the wings of insects. So next time you see a hummingbird hover under a bright sun, look closely and you may observe light shining softly through their delicate wings.
