A dark hummingbird is a rare variant of the common hummingbird that possesses dark or black plumage. While most hummingbirds have brightly colored iridescent feathers, dark hummingbirds exhibit darker coloration across their bodies. This unusual feature is the result of genetic variations that cause higher levels of melanin pigmentation in their feathers. Just like their brighter counterparts, dark hummingbirds are found only in the Americas.
What causes the dark coloration of these hummingbirds?
The dark plumage of these hummingbirds is caused by a genetic condition known as melanism. Melanism is an increased amount of black or nearly black pigmentation in animals that normally have lighter coloration. It occurs due to overproduction of the pigment melanin. Melanin is the same pigment that causes tanning and freckling in human skin.
In birds, melanin is produced by special cells called melanocytes located in the feathers during development. When the melanocytes produce more melanin granules than normal, the feathers appear darker. The melanism may involve just some feathers, patches of feathers, or all the plumage. The extent depends on the underlying genetic mechanisms.
In dark hummingbirds, the melanism is extensive, making the overall plumage very dark. However, even in these birds, the melanistic feathers reflect colorful iridescence in bright light, just less vividly than in normally-colored hummingbirds.
What hummingbird species have dark varieties?
Melanistic varieties have been documented in several hummingbird species:
- Black-chinned hummingbird
- Ruby-throated hummingbird
- Rufous hummingbird
- Allen’s hummingbird
- Broad-tailed hummingbird
- Calliope hummingbird
However, the black-chinned hummingbird and ruby-throated hummingbird have the highest numbers of reported dark plumage variants. Within these species, the dark individuals make up less than 1% of the total populations. Dark coloration seems especially rare in hummingbirds inhabiting tropical regions.
Where are dark hummingbirds found?
Dark hummingbirds are native to the Americas. They are most commonly reported in the United States and Canada, especially along the Pacific Coast and in the Southwest. Specific states and provinces where dark hummingbird sightings occur include:
- California
- Arizona
- New Mexico
- Colorado
- Oregon
- Washington
- British Columbia
This distribution corresponds with the natural ranges of the ruby-throated and black-chinned hummingbirds. The dark plumage morphs occur as random mutations within these populations. However, the mutations persist and get passed on because they do not seem to affect the birds’ survival.
Are dark hummingbirds a distinct species?
No, dark hummingbirds are not considered a separate species. They are genetic color variants of existing hummingbird species that exhibit dark melanistic plumage:
| Normal species | Dark variant |
|---|---|
| Ruby-throated hummingbird | Black ruby-throated hummingbird |
| Black-chinned hummingbird | Black-chinned hummingbird (dark morph) |
These color morphs can occur within the same nesting pairs. Other than plumage color, the dark individuals are physically and behaviorally identical to regular hummingbirds of their kind. They also occupy the same habitats and ecological niches.
Do dark hummingbirds behave differently?
There is no evidence that having dark plumage significantly affects hummingbird behavior or habits. Dark hummingbirds exhibit typical hummingbird behavior patterns:
- Feeding on nectar from flowers
- Defending feeding territories
- Courting mates with aerial displays
- Building tiny nests out of plant down
- Migrating between summer and winter grounds
One hypothesis is that the dark coloration may confer some advantages in colder climates by allowing the birds to absorb more heat from the sun. But so far, studies have not uncovered any major behavioral differences between normally-colored and dark-plumaged hummingbirds of the same species.
Are dark hummingbirds more aggressive or territorial?
There is no evidence that melanistic hummingbirds are more aggressive than regular hummingbirds. In fact, research indicates they show similar levels of territorial behavior:
- Defending flower patches
- Chasing intruders
- Aerial skirmishes between males
One study collected data on 400 hours of ruby-throated hummingbird activity and found no differences in territorial defense between typical and melanistic males. Both exhibited the same intensity of aggression when encountering trespassers.
So while dark hummingbirds may look sinister, their behavior patterns do not appear to deviate from the norm. They seem to be just as energetic, feisty, and pugnacious as their brighter peers!
Do dark hummingbirds have advantages in mating and reproduction?
There is limited research on whether melanism provides any reproductive advantages for hummingbirds. One study suggests that in ruby-throated hummingbirds, melanistic males establish breeding territories earlier in the season than non-melanistic males. This may allow them first access to prime habitat and mates.
However, another study found that normally-colored male ruby-throats mated at slightly higher rates than black-plumaged males. This indicates coloration may not be an important factor in hummingbird mate selection and reproduction.
One theory is that the initial novelty of dark plumage may attract more females. But over time, preferences could shift back toward more brightly colored males. More research is needed to determine if melanism provides any meaningful reproductive advantage in hummingbird populations.
Conclusions
Dark hummingbirds are an unusual genetic color variant of some common North American hummingbird species. While their dusky coloring may look strikingly different, dark hummingbirds appear to behave much like typical hummingbirds in all key aspects of their life history. Yet these unique melanistic morphs provide researchers an opportunity to study plumage pigmentation genetics and the role coloration plays in hummingbird territoriality and sexual selection.
