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Discovering the Enchanting World of the Black-Bellied Thorntail: A Fascinating Look at Its Traits and Survival Strategies

The avian world is filled with fascinating species, each sporting unique physical traits that make them stand out from the rest. In today’s article, we will be taking an in-depth look at the Black-bellied Thorntail, or the Discosura langsdorffi.

This stunningly beautiful bird is known for its iridescent plumage, delicate features, and dainty size. Join us as we explore the different aspects of its identification, plumage, and molts.


Field Identification

The Black-bellied Thorntail is a small bird that measures about 3.5 inches in length. The male of the species boasts a gorgeous iridescent green plumage that shimmers under the light.

Its throat and breast are black, while its belly and undertail coverts are a stunning shade of bright violet-blue. The female’s plumage is not as colorful, with greyish-brown upperparts and a white-tipped tail.

Her underparts are also pale grey, with a faint violet tinge.

Similar Species

The Black-bellied Thorntail can easily be mistaken for other closely related hummingbird species, such as the Rufous-tailed and the Fork-tailed Woodnymph. However, there are a few key distinguishing factors that set it apart from its lookalikes.

The Rufous-tailed Hummingbird has a bronze-green back and a rufous-colored tail, while the Fork-tailed Woodnymph has a black tail with white tips. The Black-bellied Thorntail, on the other hand, has a bright violet-blue undertail coverts and a black belly and throat, making it easy to identify.


The Black-bellied Thorntail has two main plumages – the breeding and non-breeding plumages. During the breeding season, which falls between January and June in their native range, the male’s plumage takes on a brilliant iridescent green hue.

The female’s plumage remains the same all year round.


The Black-bellied Thorntail undergoes a complete molt once a year, usually after the breeding season. During this time, the bird sheds its old feathers and grows new ones, a process that takes several weeks to complete.

In juveniles, the molt is partial and occurs throughout the year, as they gradually replace their downy feathers with adult plumage. In conclusion, the Black-bellied Thorntail is an enchanting bird that captures the hearts of bird enthusiasts all around the world.

Its striking plumage and charming features make it a favorite among bird watchers and photographers alike. By learning more about its identification, plumage, and molts, we can appreciate this marvelous creature and its place in the avian world.

Systematics History

The Black-bellied Thorntail, or the Discosura langsdorffi, has undergone many changes in its taxonomic classification. Initially described as a separate species in 1821, it was later included in the genus Polytmus, which was merged with the genus Discosura in 1952.

The species is currently placed in the Trochilidae family, which includes other hummingbird species.

Geographic Variation

The Black-bellied Thorntail exhibits minimal geographic variation. The species occurs in a limited area of South America, mainly in the Atlantic coastal forests of southeastern Brazil.

Though the bird is found in a relatively small range, it is also distributed in the eastern part of Paraguay and northeastern Argentina.


The Black-bellied Thorntail has only two recognized subspecies. The nominate subspecies, Discosura langsdorffi langsdorffi, is found in southeastern Brazil.

The other subspecies, Discosura langsdorffi eva, is found in eastern Paraguay and northeastern Argentina. However, some authorities consider eva as a separate species from langsdorffi.

Related Species

The Black-bellied Thorntail belongs to a group of hummingbirds known as thornbills, which are characterized by their forked central tail feathers. The genus Discosura comprises five species, including the Black-bellied Thorntail.

Among its closest relatives is the Sapphire-vented Puffleg, which is found in the Andes mountains of Colombia, Ecuador, and Peru. Another member of the genus is the Fork-tailed Woodnymph, which is found in the Amazon Basin and adjacent regions.

Historical Changes to Distribution

The Black-bellied Thorntail is currently restricted to a relatively small geographic range in southeastern Brazil, eastern Paraguay, and northeastern Argentina. However, historical records suggest that the bird was once more widespread.

Fossil remains of thornbilled hummingbirds, including the Black-bellied Thorntail, have been found in the Pliocene and Pleistocene deposits of Argentina and Uruguay. This indicates that the species may have previously had a more extensive distribution in South America.

Furthermore, the Atlantic forest, which is the Black-bellied Thorntail’s current primary habitat, has been significantly reduced in size over the past century. The forest has been progressively destroyed, resulting in habitat fragmentation that has limited the bird’s distribution.

Human activities such as logging, mining, and agriculture have significantly impacted the forest ecosystem, causing the loss of the bird’s habitat and subsequent decline in its population size. The Brazilian government has implemented conservation programs that aim to protect the remaining Atlantic forest habitat for the species and other endangered animals that rely on this ecosystem.

In conclusion, the Black-bellied Thorntail is a remarkable bird that has undergone many changes in its taxonomy and distribution. Though its range is currently limited to a small area in South America, historical records suggest that the species was once more widespread.

While the bird faces significant challenges due to anthropogenic activities, conservation efforts have been initiated to protect its remaining habitat, giving hope to the survival of this enchanting creature in the wild.


The Black-bellied Thorntail is indigenous to the Atlantic coastal forests of southeastern Brazil, where it inhabits the dense understory of the forest. The species is typically found in humid, montane, and cloud forests and is known to prefer shaded areas with an abundance of flowering bushes and plants.

It has also been observed to frequent forest edges and disturbed areas near human settlements. The bird’s habitat is located at elevations varying from sea level to approximately 3,280 feet (1,000 meters).

Movements and Migration

The Black-bellied Thorntail is generally considered a resident bird, meaning it does not undergo seasonal migrations. However, its breeding behavior exhibits irregular temporal patterns with no distinct peak in any particular month.

Studies suggest that the bird’s breeding cycle is dependent upon rainfall, which triggers the blooming of flowers and plants, a crucial food supply source for the birds. Although the species is not known to engage in long-distance migration, some individuals have been observed to undertake short movements to take advantage of seasonal resources.

During the non-breeding season, for instance, when food sources are scarce, the bird may move to lower elevations in search of fruiting trees and other primary food sources. However, this behavior is not widespread, and the species is mainly resident and confined to its preferred breeding and habitat range.

Habitat Threats

The Black-bellied Thorntail’s primary habitat, the Atlantic coastal forest of southeastern Brazil, has been identified as one of the most biologically diverse and endangered ecosystems globally. The forest has undergone significant habitat destruction due to human activities such as logging, mining, agriculture, and urbanization.

The human population has grown rapidly in Brazil, leading to an expansion of human settlements and agricultural activities at the expense of the forest. Furthermore, the forest’s ecosystem has been increasingly fragmented, limiting habitat availability and creating barriers to bird movement and dispersal.

As a result, the Black-bellied Thorntail has experienced declining population numbers over the years, and the species is currently listed as “endangered” by the International Union for Conservation of Nature (IUCN).

Conservation Efforts

Several conservation efforts have been initiated to protect the remaining habitat for the Black-bellied Thorntail and other endemic species within the Atlantic forest ecosystem. The Brazilian government has established protected areas such as national parks, biological reserves, and wildlife habitats, which have ensured the preservation of critical habitat for the bird populations.

Furthermore, efforts have been made to promote sustainable land-use practices, educate local communities on the importance of ecological conservation, and engage in habitat restoration through reforestation initiatives. International organizations and non-governmental groups have also contributed to conservation efforts.

For instance, The Nature Conservancy has partnered with local communities to implement sustainable agriculture practices that reduce deforestation and conserve the forest ecosystem. The organization has also supported forest monitoring efforts, conducted research, and developed innovative conservation policy solutions aimed at preserving biodiversity and reducing habitat loss.

In conclusion, the Black-bellied Thorntail is a remarkable bird species that depends on the unique and fragile ecosystem of the Atlantic forest for its survival. Despite the significant threats posed by human activities, conservation initiatives have been established to protect this critical habitat.

The conservation efforts offer hope for the continued survival of this delicate and beautiful bird species and other endemic fauna and flora within the rich biodiversity of the Atlantic coastal forests.

Diet and Foraging


The Black-bellied Thorntail is a nectarivorous bird, which means it feeds primarily on nectar from flowers. It has a long, curved bill that allows it to reach into flowers’ corollas to extract nectar.

The bird’s tongue is also specially designed for feeding on nectar, being long and bifurcated at the tip, which allows it to collect nectar efficiently. Additionally, the Black-bellied Thorntail consumes insects, which are a crucial source of protein and other nutrients.


The Black-bellied Thorntail feeds on a wide range of flowering plants, with a preference for those that produce large quantities of nectar. In its natural habitat, the bird feeds on flowering species such as bromeliads, epiphytes, and vines.

It has also been observed consuming nectar from non-native species such as eucalyptus and ornamental plants. The bird’s insect diet consists mainly of small flying insects such as gnats and flies.

The species hunts for insects in the air or picks them off leaves or branches while perched. It also occasionally consumes spiders and other small arthropods.

Metabolism and Temperature Regulation

The Black-bellied Thorntail has a high metabolic rate and a body temperature that fluctuates throughout the day. To maintain its high metabolic activity, the bird requires a constant source of energy and undergoes frequent feedings throughout the day.

The bird’s high metabolic rate also permits it to maintain a high body temperature, which enables the bird to thrive in its natural habitat.

Sounds and Vocal Behavior


The Black-bellied Thorntail’s vocal behavior is mainly observed during breeding season and is an essential aspect of the bird’s social behavior. The male bird makes a unique sound during courtship, which is known as a humming or whirring sound.

This sound is generated by the bird’s wings flapping at an extremely high rate, producing a distinctive sound that is important for courtship displays. In addition to vocalizing during courtship, the Black-bellied Thorntail also produces a faint chirping sound, which is often heard when the bird is feeding or perched.

The chirping sound is generated by the bird’s beak and is believed to be a communication tool within the species. However, the chirping sound is not as loud as that produced by other hummingbird species, and it is often overshadowed by the sound of the bird’s wings flapping.


The Black-bellied Thorntail is a unique bird species that is well adapted to its natural habitat. Its feeding behavior is specialized, with a preference for nectar from flowers and small insects.

The bird’s metabolic rate, which is high, allows it to maintain its constant activity, while its body temperature fluctuates throughout the day. Furthermore, the bird’s vocal behavior is predominantly observed during courtship displays and when feeding or perched.

While the bird’s chirping sound is a form of communication among its species, its courtship hum or whir is an important aspect of its social behavior during breeding season. Overall, the Black-bellied Thorntail is a fascinating bird species with unique traits that make it stand out among hummingbird species.



The Black-bellied Thorntail is an agile and fast flyer. It uses its wings to hover in place while feeding on floral nectar, a behavior typical among hummingbird species.

The bird’s wings are short and rounded, which makes it highly maneuverable in flight. When perched, the bird assumes an upright posture, which reduces the drag caused by air resistance.

Self Maintenance

The Black-bellied Thorntail is very active during the day, with high metabolic rates and intensive flight activity. In addition, the bird requires frequent feeding to maintain its energy levels.

While perched, the bird engages in self-maintenance activities, such as preening, stretching and cleaning its feathers, and often ruffling its plumage.

Agonistic Behavior

The Black-bellied Thorntail is known to exhibit agonistic behavior, particularly during feeding and courtship. The male bird defends its feeding territory against rivals through aggressive behavior that involves aerial displays, chasing, and vocalizations to assert dominance.

Females have also been observed participating in aggressive behavior with other females when defending feeding territories.

Sexual Behavior

The Black-bellied Thorntail’s breeding behavior involves courtship displays and intricate social interactions. The males perform courtship flights, hovering and diving while generating the humming sound created by their wings.

They also display through wing and tail feather flapping, showing off the brilliant iridescent colors of their feathers. The females select their mates based on their courtship displays and mating behavior.


The Black-bellied Thorntail’s breeding season is irregular, with no distinct peak of breeding activity in any particular month. The breeding cycle is triggered by rainfall and the blooming of flowers and plants.

Males establish territories within their preferred breeding habitat and defend these areas aggressively against other males. Females establish feeding territories, and a male’s access to these territories is a critical factor in determining his breeding success.

The female Black-bellied Thorntail builds a small, cup-shaped nest out of soft plant materials, lichens, and spider silk. The nest is typically placed on the underside of leaves around 5-9 feet (1.5-2.7 meters) off the ground.

The female lays two tiny eggs, which are white and marked with pink or brown speckles. The incubation period lasts around two weeks, and the chicks hatch blind and naked.

The chicks are fed regurgitated nectar and small insects by the mother. They remain in the nest for around three weeks until they fledge, at which time they are fully feathered and able to fly.

The Black-bellied Thorntail breeds once per year.

Demography and Populations

The Black-bellied Thorntail is considered an endangered species, primarily due to habitat loss and fragmentation. The bird’s primary habitat, the Atlantic coastal forests of southeastern Brazil, has been reduced to less than ten percent of its original size over the past century.

This severe habitat loss has led to a significant reduction in the bird’s population size and genetic diversity. Conservation efforts have been initiated to protect the remaining habitat for the Black-bellied Thorntail.

The bird’s limited distribution and population size have made it difficult to estimate population numbers accurately. However, studies suggest that the bird’s declining population trend may be slowing down due to conservation initiatives, including reforestation, habitat protection, and sustainable land-use practices.

In conclusion, the Black-bellied Thorntail is a unique and remarkable bird species that has evolved specialized adaptations to its habitat and behaviors. Its breeding and social behavior, agonistic interactions, and courtship displays are intricately linked to its survival strategy.

The bird’s population size, however, is currently threatened due to habitat loss and fragmentation. While conservation efforts have been initiated to protect this species and its habitat, more must be done to ensure the continued survival of this beautiful bird.

The Black-bellied Thorntail is a captivating bird that has evolved many remarkable traits and behaviors. Its unique adaptations to its habitat, such as its specialized feeding, breeding, and social behaviors, highlight the importance of preserving the bird’s habitat and ecosystem.

Habitat loss and fragmentation due to anthropogenic activities such as logging, mining, and agriculture have led to a significant reduction in the bird’s distribution and population size. Conservation initiatives have been established to protect the remaining habitat, restore degraded ecosystems, and promote sustainable land-use practices.

The continued efforts to conserve this and other endangered species are essential to safeguarding our planet’s biodiversity and preserving its delicate ecological balance.

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