Coppery Thorntail—One of the Most Mysterious Hummingbirds

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A bird about which almost nothing is known

The coppery thorntail is known from only two male museum specimens. Only fragmentary information survives about where and when the two birds were found: The type specimen must have been collected before the scientific description was published in 1852, while the collection date of the second specimen is unknown. Although Bolivia was given as the place of origin, even this information is considered uncertain.

It is also no longer possible to determine when the coppery thorntail was last recorded alive. The second known skin was reliably documented by 1878 at the latest, when the ornithologist Daniel Giraud Elliot mentioned it as part of his collection. Since then, no further specimen has come to light. Nor is there any reliable report of a living bird having been observed. We know virtually nothing about the species’ habitat or way of life—even the appearance of the females is unknown.

The British ornithologist Julian P. Hume (2017) describes the coppery thorntail as “probably extinct”. John C. Mittermeier et al. (2022), by contrast, include it in a small group of especially enigmatic Neotropical bird species known as Mysteries. For these species, further investigation of historical sources and old museum specimens may be needed to clarify their origin, taxonomic status, and perhaps even their fate.

The story of the coppery thorntail begins—and, for the time being, ends—with two old bird skins in European and American museum collections.

Coppery thorntail – profile

alternative names	Letitia’s thorntail, Letitia’s coquette
scientific names	Discosura letitiae, Popelairia letitiae, Gouldia laetitiae, Trochilus letitiae, Prymnacantha letitiae
range	unclear, possibly Bolivia (South America)
date of disappearance	unknown, probably in the 19th century
possible threats	unknown
IUCN status	Data Deficient

The two known specimens

The type specimen of the coppery thorntail is now held at the Natural History Museum in Tring (BMNH 1888.7.25.83). It originally belonged to the French ornithologist Jules Bourcier, who scientifically described the bird together with Étienne Mulsant in 1852. The specimen later entered the collection of the British ornithologist John Gould and ultimately that of the then British Museum (Graves, 1999).

The second specimen is held at the American Museum of Natural History in New York (AMNH 38060). It belonged to the collection of Daniel Giraud Elliot and was reliably documented by 1878 at the latest. The label of the New York specimen bears the notation “Verreaux”. In the 19th century, the brothers Jules and Édouard Verreaux ran a major natural history specimen dealership in Paris.

A new hummingbird from “Bolivia”

In 1852, the French naturalists Jules Bourcier and Étienne Mulsant provided the first scientific description of the coppery thorntail. In a paper presenting several new hummingbird species, they named it Trochilus letitiae. The authors gave only the terse designation “Bolivia” for the bird’s origin—they provided no more precise locality, collection date, or information about its habitat.

Only several years later did John Gould reveal that Bourcier had possessed just this one specimen, on which the original description was therefore based. Gould referred to the bird as Bourcier’s “unique specimen” and was permitted to examine and illustrate it for his major monograph on hummingbirds (1861). This skin from Bourcier’s collection is the type specimen now held in Tring. Who originally collected the bird or obtained it for Bourcier is unknown (Graves, 1999).

Gould explained why his plate published in 1855 shows two birds:

“Regrettably, the female remains unknown; I have therefore depicted the male in two positions on the plate.”

The original description of 1852 is essentially limited to the external features and measurements of the preserved specimen. Among other characteristics, Bourcier and Mulsant described the glossy green plumage on the head and underparts, the gold-to-copper sheen of the upperparts, the white band on the rump, and the color and shape of the tail. They gave the total length as about nine centimeters. Gould (1855) later highlighted in particular the entirely glossy head, the comparatively short tail, and its pointed outer tail feathers.

The original description also explains the specific epithet letitiae. Bourcier and Mulsant dedicated the bird to Letizia del Gallo Roccagiovine (1848–1863), a granddaughter of the renowned ornithologist Charles Lucien Bonaparte. She was also a great-grandniece of Napoleon Bonaparte.

Is the coppery thorntail even a distinct species?

Only two old museum specimens of the coppery thorntail are known. Although its status as a distinct species was widely accepted for a long time, several similarly rare hummingbird forms known only from individual specimens were later shown to be hybrids or unusual variants of other species. In the late 1990s, this prompted the American ornithologist Gary R. Graves to fundamentally reassess the taxonomic status of the coppery thorntail.

In his 1999 study, Graves examined four possibilities: The two birds might represent the juvenile plumage of the racket-tipped thorntail (Discosura longicaudus), a geographic variant of that species, hybrids, or actual representatives of a distinct species. To investigate, he compared their plumage color, body measurements, and the shape of individual feathers with those of other thorntails and related hummingbirds.

Graves first determined that both known specimens are males in definitive adult plumage. Evidence includes the glossy throat and crown feathers and the elongated tail feathers. This ruled out the idea that the coppery thorntail might merely represent the juvenile plumage of the racket-tipped thorntail.

Although the coppery thorntail clearly resembles the racket-tipped thorntail, it differs markedly from it in several features. The coppery thorntail, for example, lacks the racket-tipped thorntail’s black chin patch; its back and rump are more strongly copper to bronze in color; and its outer tail feathers have a different shape. The wings and tail feathers are also significantly shorter. According to Graves (1999), these differences exceed the usual geographic variation within comparable hummingbird species. He therefore regards the coppery thorntail as neither a juvenile nor a regional form of D. longicaudus. Instead, the strong similarity between the two birds may indicate that they are closely related or even sister species.

Graves also found no convincing evidence that it arose through hybridization. His comparison included various thorntails and coquettes (Lophornis) as possible parent species. No conceivable combination, however, could explain the complete set of features found in the coppery thorntail. For example, it lacks plumage traits that would be expected if certain Lophornis species had been involved, while other potential parent species have much longer outer tail feathers.

Further support for its status as a distinct species comes from the fact that the two coppery thorntails are remarkably similar to each other. Their wing lengths differ by only about 0.5%; their plumage patterns and coloration also match down to small details such as the feathering of the legs and the undertail coverts. According to Graves (1999), the differences between the two specimens fall within the normal individual variation of hummingbirds. By contrast, two independently occurring hybrids with such a similar combination of features would be difficult to explain.

Graves therefore concluded that the coppery thorntail should be regarded as a distinct species unless contradictory evidence emerges. Today, too, Discosura letitiae is treated as a distinct species in the leading taxonomic checklists.

Graves (1999) also proposed changing the English common name to Letitia’s Coquette. He felt that the shape of the tail feathers was more reminiscent of the so-called coquettes—small, often strikingly ornamented hummingbirds primarily in the genus Lophornis—than of typical thorntails. Graves did not intend this to place the coppery thorntail taxonomically in Lophornis; his proposal concerned only the English name and the unusual tail shape.

Even so, the question has not been fully resolved. Graves’ study was based on plumage traits, feather shapes, and body measurements. No genetic data are yet available for the two museum specimens (Foster, 2025). Modern DNA analyses could provide the first genetic test of Graves’ morphological classification and reveal where the coppery thorntail actually belongs within the thorntails.

From Trochilus to Discosura

When Bourcier and Mulsant described the coppery thorntail in 1852, they initially placed it in the very broadly defined genus Trochilus. Even then, they noted similarities to Trochilus conversii—today’s green thorntail (Discosura conversii). The original describers had thus already recognized an affinity with the group of hummingbirds to which the coppery thorntail is still assigned today.

Its generic placement changed several times over the following decades. John Gould listed the species as Gouldia laetitiae; later, it was assigned together with several other thorntails to the genus Popelairia. Graves (1999) noted that Popelairia could not be retained under nomenclatural rules if merged with Discosura: Popelairia Reichenbach, 1854 is younger than Discosura Bonaparte, 1850 and would therefore become its junior synonym.

Accordingly, the coppery thorntail is now called Discosura letitiae. The genus also includes the green thorntail (D. conversii), black-bellied thorntail (D. langsdorffi), wire-crested thorntail (D. popelairii), and racket-tipped thorntail (D. longicaudus).

Based on their strong external similarity, Graves (1999) suspected that the coppery thorntail and the racket-tipped thorntail might be sister species—that is, especially close relatives. Whether this hypothesis can be confirmed genetically remains unknown.

Where did the coppery thorntail live?

Where the two known coppery thorntails were collected remains a mystery to this day. In their original description, Bourcier and Mulsant (1852) gave only “Bolivia” as the place of origin. They provided no more precise locality or further details. The labels on the two surviving museum specimens likewise provide no more exact information about their origin.

In addition, political borders in the region have changed since the 19th century. Areas of the Amazon region that were once considered part of Bolivia now belong to Brazil (BirdLife International, 2023). Even if the historical designation “Bolivia” was broadly correct, it therefore need not correspond precisely to the modern territory of Bolivia.

Graves (1999) emphasized that even the country designation might be uncertain. Locality data on 19th-century hummingbird skins were not always reliable. A particularly vivid example can even be found in the same publication in which the coppery thorntail was described: Bourcier and Mulsant stated that the hook-billed hermit (Ramphodon dohrnii) came from Ecuador. Today, however, we know that this species occurs in Brazil’s Atlantic Forest. Graves therefore warns against restricting any search for the coppery thorntail to Bolivia alone.

Nevertheless, there has been speculation about where the species might have lived. In 1989, James V. Remsen and Melvin A. Traylor suggested northeastern Bolivia as a possible place of origin. Joseph A. Tobias and his team, writing in a 2006 article, considered the then still comparatively little-known lowland forests of northern and northeastern Bolivia especially plausible. The ecology of related species offers at least some support for this idea: The black-bellied thorntail, another member of the same genus, occurs in the western Amazonian lowlands, including northern Bolivia, and three of the four other Discosura species also inhabit lowland regions or their margins. This could indicate that the coppery thorntail was adapted to such habitats as well.

If the coppery thorntail still exists, Tobias et al. (2006) suspected that it would occur primarily in the upper forest strata and along the edges of primary and secondary forests. They therefore recommended scrutinizing thorntails particularly carefully not only in Bolivia itself, but throughout the Amazonian lowlands and adjacent foothills around Bolivia.

More recent studies remain similarly cautious. In 2020, Thomas Züchner, Peter F. D. Boesman and Christopher J. Sharpe emphasized that the distribution of the coppery thorntail remains unresolved because of the uncertain origin of the two known specimens. It therefore cannot be ruled out that the species occurred outside Bolivia or may still exist undiscovered.

When was the species last recorded?

The type specimen on which the original description was based must have been collected in 1852 or earlier. The collection date of the second known specimen, by contrast, is unknown. This skin has been reliably documented since 1878. At that time, Daniel Giraud Elliot wrote about the coppery thorntail in A classification and synopsis of the Trochilidae:

“Only two specimens of this species have been obtained; one is in my collection and one in that of Mr. Gould.”

We do not know when Elliot obtained his specimen or when the bird was actually collected. Nevertheless, Tobias et al. (2006), Hume (2017), and other recent sources state that both specimens had been collected before 1852. Martin et al. (2023) give 1852 as the last record, while Kittelberger et al. (2024) give 1851. The sources reviewed to date do not reveal the basis for dating the second specimen to before 1852. Graves (1999) gives no collection date for the New York skin; it is unequivocally documented in the literature only by Elliot (1878).

The manner in which the two birds were prepared offers one possible indication that they originated at around the same time. Graves (1999) found that both skins were prepared in a very similar taxidermic style. The New York specimen also bears the notation “Verreaux.” The two specimens may therefore have come from the same circle of the Verreaux brothers’ natural history trade in Paris. This does not, however, allow us to conclude either that the two birds were collected together or that the second specimen was also collected before 1852.

An exact year for the last record of the coppery thorntail therefore cannot be given. All that is certain is that the last known evidence dates from the 19th century.

Extinct or still lost?

Whether the coppery thorntail still exists today cannot currently be answered. No new reliable record of the species has become known since the 19th century. There are no photographs, sound recordings, or more recent museum specimens. The Search for Lost Birds project therefore continues to list it as a “Lost Bird” and gives 1852 as the last documented record. However, “lost” is not an official conservation category; here it refers to bird species that have not been reliably documented for at least ten years.

The fact that no other bird has been found over such a long period suggests that the species may be extinct. Several authors accordingly describe it as “probably extinct,” thus considering it likely extinct (Hume, 2017; Maillard et al., 2022). The available data are not sufficient, however, for a formal classification as extinct. The IUCN lists the coppery thorntail as Data Deficient (DD)—meaning that there is insufficient information to assess its conservation status reliably (BirdLife International, 2023). Adams and Berryman (2026) likewise continue to list it in their current review of extinct and endangered bird species as Data Deficient.

The unusually long period without a record is especially difficult to assess for this species because not even the precise collection locality of the two known specimens is known. They are said to have come from “Bolivia,” but even this information is considered uncertain. This means that a crucial prerequisite for a targeted search is missing: We know neither where to search for the species nor what habitat it occupied. Discosura letitiae may even have occurred outside present-day Bolivia.

A digital search for the lost coppery thorntail

In 2022, John C. Mittermeier and his colleagues systematically searched for modern evidence of lost bird species in the Neotropics. They began with observations on eBird and media in the Macaulay Library. For species lacking recent evidence, the researchers also searched Xeno-canto, WikiAves, iNaturalist, Google Scholar, and Google for verifiable photographs, sound recordings, or indications of genetic material.

The search for the coppery thorntail produced no results. Mittermeier et al. (2022) found no modern media evidence and assigned it, along with three other species, to a group of especially enigmatic Mysteries. In addition to the coppery thorntail, these include the Cayenne nightjar (Setopagis maculosa), white-tailed tityra (Tityra leucura), and Duida grass finch (Emberizoides duidae). These species share the fact that they are known only from a few specimens or incomplete historical information and are classified as Data Deficient.

The researchers emphasize that for such species, field searches alone may not be sufficient. Museum and archival research could help clarify their true origin and taxonomic status. Some comparable cases may ultimately prove to be hybrids or subspecies. At the same time, advances in the genetic analysis of old museum skins could help solve such centuries-old mysteries.

Why might the coppery thorntail have become extinct?

Nothing is known about possible causes for the disappearance of the coppery thorntail. Because neither its actual range nor its habitat is known with any certainty, it is also impossible to reconstruct the threats the species may have faced.

BirdLife International (2023) accordingly notes that possible threats have not been studied. However, if the coppery thorntail did indeed live in Amazonian lowland forests and still occurs there, it could be threatened by habitat loss. This is a hypothesis about a possible surviving population—not a demonstrated cause of the species’ disappearance.

Between hybrids, synonyms, and lost species

Especially during the 19th and early 20th centuries, numerous new hummingbird taxa were described from one or a few museum specimens. Some were later found not to be distinct species, but synonyms of species already known or hybrids. The Recently Extinct Plants and Animals database lists several hummingbirds originally described as distinct forms that are now considered hybrids, including the Táchira emerald (Amazilia distans), Isaacson’s puffleg (Eriocnemis isaacsonii), green-throated sunangel (Heliangelus squamigularis), and Bogotá sunangel (H. zusii).

This does not mean that hummingbirds are inherently especially difficult to distinguish from one another. Rather, the problem was often the extremely small basis for comparison. With a single old skin, it is difficult to determine whether unusual traits truly characterize a distinct species or result from age, sex, individual variation, or hybridization. Compounding the problem is the metallic, iridescent plumage of many hummingbirds, whose color can change depending on the angle of the light. Moreover, in the case of historical trade skins, even the place where the birds had been collected was sometimes not reliably known.

Generic placement was likewise based primarily on external features for a long time; particularly striking plumage structures in males played a major role. The classification used by Graves (1999) at the time distinguished 109 hummingbird genera, more than a quarter of which contained only a single species. Later phylogenetic studies led to the reassessment of many of these generic boundaries.

Assessing very rare hummingbirds is further complicated by the fact that a decades-long absence of records does not necessarily mean extinction. For example, the Vilcabamba Inca (Coeligena eisenmanni) was documented in 2024 for the first time since 1967. And two years earlier, the Santa Marta sabrewing (Campylopterus phainopeplus) was rediscovered after the species had last been seen in 2010. Rediscoveries such as these make clear that even decades without records do not necessarily mean that a species has disappeared.

On the other hand, several hummingbirds have histories with striking parallels to that of the coppery thorntail. Brace’s emerald (Riccordia bracei) is known only from a single skin collected on New Providence in 1877. Likewise, only one specimen of Gould’s emerald (R. elegans) exists, and its precise origin is unknown. Amazilia alfaroana is also known only from the 1895 holotype. For a long time, there was debate over whether this bird represented a distinct species at all or was instead a hybrid; after reexamining it, Kirwan and Collar (2016) concluded that it was best regarded as a distinct species that may now be extinct.

Another parallel is provided by the turquoise-throated puffleg (Eriocnemis godini). Bourcier described it in 1851, only one year before the coppery thorntail. This species, too, is known only from a few historical museum specimens. Of the six known specimens, only the type, collected in 1850, has a reliable locality from northern Ecuador; other specimens entered European collections as so-called “Bogotá” trade skins. There has been no confirmed record since the 19th century, apart from an unconfirmed observation in 1976.

The coppery thorntail is therefore by no means an isolated case. Some hummingbirds are known only from one or a few historical specimens of partly uncertain origin. Other supposed species were later shown to be hybrids or synonyms, while still others were unexpectedly rediscovered after decades. Such cases demonstrate how difficult it is to reach a final verdict on the coppery thorntail: Two museum skins prove that this hummingbird existed—but they reveal almost nothing about where it lived, how it was related to other hummingbirds, or whether a population might still survive somewhere.

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