Hummingbirds are known for their iridescent plumage, with many species having brightly colored feathers on their throats or crowns. Male hummingbirds in particular often have elaborately colored throats that they display during courtship rituals. However, this adult plumage develops over time, so young juvenile hummingbirds look quite different from their mature counterparts. This raises an interesting question: do juvenile male hummingbirds have red throats like the adults? Or do they start out with a different appearance that changes as they mature? In this article, we’ll explore what is known about the development of hummingbird plumage from juveniles to adults, focusing on male throat coloration. Understanding these changes can provide insight into hummingbird growth, evolution, and mating strategies.
Plumage Differences Between Juvenile and Adult Hummingbirds
There are over 300 different species of hummingbirds throughout the Americas, displaying an incredible diversity of colors and plumage patterns. Adult male hummingbirds are often particularly striking, with bright metallic gorgets (throat patches) in shades of crimson, fuchsia, orange, blue, or green. The most common species in North America, like Ruby-throated Hummingbirds and Allen’s Hummingbirds, have vivid red throats when mature. On the other hand, female and juvenile plumage is less vividly colored, with more subdued throats in white, grey, or light green. Their goal is not to attract attention.
These differences reflect the variation in evolutionary pressures acting on adult male versus female/juvenile hummingbirds. Adult males must attract females for mating through conspicuous visual displays, leading to the evolution of bright plumage. In contrast, females and juveniles are more vulnerable to predation when incubating eggs or caring for young. Their cryptic coloration provides camouflage and avoids attention from predators.
The differences between mature adult and juvenile male hummingbird plumage presents an opportunity to study how sexual selection shapes ornate feathers used in courtship over the course of maturation. Next, we’ll take a closer look at the details of male hummingbird development.
Throat Color Changes in Juvenile Male Hummingbirds
At hatching, both male and female hummingbird chicks have similarly camouflaged plumage without any bright coloration. Their tiny bodies are covered in grey or brown down feathers. The young birds leave the nest at around 3 weeks old, but still lack any distinguishing colors.
Over the next few weeks, the young hummingbirds molt and start growing in their first set of true feathers. In males of species like Ruby-throats, Allen’s, Rufous, and Anna’s Hummingbirds, these juvenile feathers include some iridescent throat patches. However, the patches are usually a conspicuous green, orange, or yellow, unlike the red of adults. This indicates the throat feathers are still developing their structural coloration.
One study on Ruby-throated Hummingbirds measured the reflectance of juvenile male throat feathers compared to adults. They found the nanostructures responsible for color were still forming in the young birds. Over the first year of life, the throats gain more organized layers that reflect red wavelengths. By their first breeding season about one year old, males complete their molt to acquire the full adult red throat gorget.
Researchers believe female preference for red mating displays drives the evolution of these structured feathers. The color acts as an indicator of male fitness. Only the healthiest, most vigorous males can fully develop the elaborate patches.
Why Do Juvenile Males Have Different Throat Colors?
Since the red throats are used to attract females, why wouldn’t juvenile males also display them? There are a few potential explanations scientists have proposed:
Physiological Constraints
Producing the highly structured feathers requires energy and nutritional resources. Juvenile birds may not be able to invest as much into feather development as adults while they are still growing. Instead, they start with simpler green or yellow throat feathers when young. By restricting the red gorgets to adults, the feathers can act as an honest signal of male quality and condition.
Avoiding Aggression from Adult Males
In some bird species, adult males react aggressively to juveniles with more elaborate plumage. The young birds may be perceived as mating competition. Having a distinctly different appearance as a juvenile may help reduce aggressive attacks from older territorial males. This increases juvenile survival until they are mature enough to compete for mates.
Female Choice for Adult Plumage
Females may have an innate preference for the red throats of mature males. Even if juveniles developed full gorgets, females might still choose to mate with older birds with more courtship experience. The different throat color reinforces their adult status.
More research is still needed to determine the exact factors that prevent juvenile males from matching adult male plumage. But in general, delaying full maturation of visual displays seems to benefit both juvenile survival and honest advertisement of male quality. Next we’ll compare the throat patch color changes across some common North American hummingbird species.
Comparing Throat Colors of Juvenile Male Hummingbirds by Species
Here is an overview of what we know about throat color development in a few common North American hummingbird species:
Ruby-throated Hummingbird
- Adult males: Vivid red throat gorget
- Juvenile males: Mostly white throat with some orange spotting. First red feathers around 6-9 months old.
Rufous Hummingbird
- Adult males: Bright orange red throat
- Juvenile males: Speckled orange throat, brighter yellow closer to bill
Allen’s Hummingbird
- Adult males: Red throat and green crown
- Juvenile males: Yellow green throat, resembles adult female
Anna’s Hummingbird
- Adult males: Iridescent rose red throat and crown
- Juvenile males: Grey throat with some reddish spotting
Costa’s Hummingbird
- Adult males: Vibrant purple throat
- Juvenile males: White throat with small purple spotting
The details vary by species, but a consistent pattern emerges. Juvenile male hummingbirds have markedly different throat colors compared to adults, lacking the bold reds, oranges, or purples of mature plumage. This supports the idea that delayed maturation of these visual displays provides some benefit to the birds.
Do Female Hummingbirds Also Show Age-Related Throat Color Changes?
While juvenile male hummingbirds have strikingly different throat colors compared to adult males, female hummingbird throat plumage shows less dramatic age-related changes.
In many species like Ruby-throated, the mature female has a solid white throat. Juvenile females similarly have white throats from a very early age, sometimes with some faint grey spotting. Because they lack elaborate mating displays, juvenile female throat color is not under the same selective pressure to develop over time.
Here are some examples of similarities between juvenile and adult female throat plumage:
Ruby-throated Hummingbird
- Adult females: Solid white throat
- Juvenile females: Mostly white throat
Allen’s Hummingbird
- Adult females: Pale grey-green throat
- Juvenile females: Light grey throat
Rufous Hummingbird
- Adult females: White throat with dark spotting
- Juvenile females: White mottled throat
Conclusion
In summary, the answer to whether juvenile male hummingbirds have red throats is generally no. Young males have distinctly colored yellow, green, white, or orange throats that contrasts with the red, fuchsia, or purple of adults. This may reflect physiological constraints, reduce aggression from older males, or increase female preference for adult plumage. In comparison, female throat plumage shows minimal age-related differences between juveniles and adults across species. Understanding development of hummingbird throat feathers provides insight into how evolution shapes ornate mating displays over the course of maturation. Continuing research in this area will shed light on the selective pressures driving hummingbird ornamentation and mating strategies.
