Tongatapu Rail

The only specimen is now lost

Many bird species from the past were described based on a single specimen, which is now lost. One such example is the Tongatapu rail. Historical reports and descriptions of this bird species from the rail family (Rallidae) remain, based on observations and collections made during the voyages of the English explorer James Cook in the 18th century.

When Cook and his expedition ships reached the island of Tongatapu in the Kingdom of Tonga in the South Pacific in June 1777, William Anderson, a Scottish naturalist and surgeon, recorded a variety of birds that were collected by the locals and sold to the sailors. Among these were pigeons, small rails, and purple swamphens.

During this third voyage, the German naturalists Reinhold and Georg Forster also encountered a specimen of the Tongatapu rail on the main island of the Tonga archipelago. The well-known English naturalist and President of the Royal Society, Joseph Banks, acquired the skin of the bird, which was likely preserved in alcohol. This specimen was the only one documented in scientific collections. It was mentioned in the Solander Catalogue as part of the Banks Collection and described in Manuscript List 3 as Rallus spectabilis. Unfortunately, this specimen is now lost.

There is speculation that this specimen may have been among those that Joseph Banks distributed in 1792 to significant institutions like the British Museum and the British physician and naturalist John Hunter. Banks aimed to make his extensive natural history collection accessible to the scientific community even after his death, ensuring that the specimens would be preserved and serve research purposes. However, the limited documentation and preservation techniques of the time, along with the challenges of handling delicate natural history specimens, likely contributed to the loss of some specimens over time.

Incidentally, during the third South Sea voyage, Cook and his crew also discovered the now-extinct Kiritimati sandpiper. Like the Tongatapu rail, the only known specimen of this bird, which also became part of Joseph Banks’s collection, is now lost.

The scientific descriptions and catalogue entries created by Banks and his colleagues are now the only physical evidence of the existence of the Tongatapu rail. However, there is also a contemporary painting by Georg Forster, created during Cook’s second South Sea voyage between 1772 and 1775, which was often thought to depict the lost Tongatapu Rail. This assumption is questionable, as the Tongatapu rail was not discovered until 1777. Some experts therefore believe that Forster actually depicted Gallirallus philippensis ecaudatus, a subspecies of the buff-banded rail. This depiction might have been made not on the island of Tongatapu but on the smaller island of Nomuka, which also belongs to the Polynesian island nation of Tonga.

Tongatapu Rail – Fact sheet

Scientific name	Hypotaenidia hypoleucus, Gallirallus hypoleucus, Rallus hypoleucus, (Rallus spectabilis)
Original range	Tongatapu (South Pacific)
Time of extinction	1777 at the earliest
Causes of extinction	habitat loss, animals introduced to the island, hunting

Was James Cook responsible for the extinction of the Tongatapu rail?

James Cook and his crew may have indirectly contributed to the extinction of the Tongatapu rail, particularly through the introduction of dogs to the Tonga Islands in October 1773. In his journal, Cook documented that he left dogs on Tongatapu and Nomuka: “I also left a young dog and a bitch; animals they have not, and which they are very fond of.”

William Anderson, who accompanied Cook on his third Pacific voyage, reported five years later that he found a significant number of feral dogs on Tongatapu. Dogs are known and effective predators, hunting both eggs, young birds, and adult birds, especially when these birds are poor or non-flyers. The British ornithologist Julian P. Hume writes in Extinct Birds (2017) that the Tongatapu rail, “like so many island rails, it was probably at best only poor volant.” This suggests that the introduced dogs could have caused a significant decline in the population of the ground-nesting Tongatapu rail.

It would be unreasonable to hold Cook’s expeditions solely responsible for the extinction of the Tongatapu rail, but it is likely that the introduction of dogs played a role in their decline.

Possible reasons for the extinction of the Tongatapu rail

While Cook and his crew undoubtedly had an impact on the ecosystems of the Tonga Islands, it is unlikely that they alone were responsible for the extinction of the Tongatapu rail. The decline of this species was likely the result of a combination of several factors:

Introduction of invasive species: Pigs, rats, and cats

In addition to the dogs introduced by Cook, other predatory species like pigs and rats had been brought to the Tonga Islands long before his arrival by Polynesian settlers. Pigs, being omnivores, pose a significant threat to ground-nesting birds as they root through the soil in search of food, often destroying bird nests and eating eggs and young birds in the process. A 1990 study by Linda W. Cuddihy and Charles P. Stone demonstrated that pigs can alter the structure of ecosystems and contribute to the extinction of various native species. These changes affect both animals and plants, as pigs uproot vegetation and disturb the soil.

Rats, often accidentally introduced to islands, have also led to the decline and extinction of many island bird species, particularly ground-nesting ones. Cats, brought to the Tonga Archipelago by European explorers, have spread across nearly all the Tonga Islands. Feral house cats are known as versatile predators, preying on eggs, chicks, and adult birds, as well as amphibians and reptiles.

The combination of the introduction of dogs, pigs, rats, and cats likely led to a significant decline and ultimately the extinction of the Tongatapu rail through predation and habitat destruction. These predators disrupted the balance of the island ecosystem, putting particular pressure on ground-nesting birds like the rail.

A similar fate befell the Tongan ground skink, which was endemic to Tongatapu and disappeared in the early 19th century. It is believed that predation by introduced animals and the loss of its natural habitat were the main causes of its extinction.

Habitat changes: Deforestation and agriculture

Before human settlement, the Tonga Islands were densely forested, offering a variety of habitats, particularly for ground-nesting species like the Tongatapu rail. These lush forests were crucial for the survival of native species. However, with the arrival of Polynesian settlers around 2,800 years ago, large-scale deforestation began to make way for the cultivation of crops such as taro, yams, and bananas. This deforestation led to the fragmentation of forests and the destruction of essential habitats for the native fauna.

When Cook arrived on the island of Tongatapu in the late 18th century, he found that most of the island was already under agricultural use and covered with plantations. In a 1993 study on the birds of Tonga before and after human settlement, the American paleozoologist David W. Steadman aptly summarized the situation:

“The arrival of humans has influenced the Tongan avifauna more than any climatic, tectonic, or biological event of the past approximately 100,000 years.”

Biogeography of Tongan Birds Before and After Human Impact. PNAS 1993. D. W. Steadman.

The arrival of Europeans in the Kingdom of Tonga further intensified these changes through the introduction of new agricultural practices, monoculture farming, and the cultivation of commercial crops such as sugarcane and coconut palms. The resulting destruction of forests likely led to the loss of critical feeding and breeding sites for the Tongatapu rail. As a ground-nesting bird, this species relied on dense vegetation to build its nests and protect its young from predators. Steadman emphasizes that the loss of forest habitats was one of the main reasons for the extinction of many Polynesian bird species, including rails.

Trade and collection of live birds

Hunting and other human disturbances undoubtedly played a significant role in the decline and eventual extinction of the Tongatapu rail. On isolated Pacific islands, where species often have no natural predators and show little fear of humans (island tameness), ground-nesting, flight-limited birds like the Tongatapu rail are particularly vulnerable to anthropogenic influences and hunting.

Since their arrival on the Tonga Archipelago, Polynesian settlers hunted native birds as a food source. This practice continued for centuries and likely contributed to a continuous decline in rail populations. The visits of James Cook and other European explorers further intensified hunting pressure, as they introduced new technologies and methods that increased the efficiency of hunting. Cook mentioned in his journals that his crew hunted various birds, including rails, during their stays on the Tonga Islands.

Additionally, the trade in live birds was a common practice among the Tongans, particularly during the visits of European ships. The locals often brought rare bird species on board to sell to the sailors. This trade could have significantly contributed to the decimation of the Tongatapu rail populations, as many birds were captured and removed from their natural habitat. It is documented that the Tongans regularly offered birds for sale to Cook and his crew, further increasing the pressure on the already vulnerable populations.

When did the Tongatapu rail go extinct?

After the discovery of the Tongatapu rail in 1777, no further sightings of this bird species were recorded, leaving the exact date of its extinction undocumented. However, most experts, including New Zealand ornithologist David G. Medway in The Tongatapu Rail Gallirallus hypoleucus – an Extinct Species Resurrected? (2010), believe that the species likely became extinct by the end of the 18th century.

According to Medway, by the 1770s, Tongatapu Island was already an unfavorable habitat for rail birds, especially those that were nearly flightless. The island had been inhabited by humans for nearly 3,000 years by that time, and much of its original forests had been cleared, as noted by Steadman in Extinction & Biogeography of Tropical Pacific Birds (2006).

Steadman, Medway, and Hume all find it somewhat surprising that the Tongatapu rail survived into the 1770s at all. The bird had to endure centuries of hunting by locals, habitat destruction, and pressure from introduced mammals. The dogs introduced by Cook were likely just the final, decisive factor that led to the species’ ultimate extinction.

Tongatapu rail: Discovered in 1777, recognized as a distinct species in 1867

The English ornithologist John Latham had access to the animal specimens collected by Joseph Banks during James Cook’s voyages in the South Seas. The specimen of the Tongatapu rail served as the basis for Latham’s detailed description of the bird in 1784. He emphasized the distinctive plumage features that set this bird apart from other rail species.

“The head in this variety is paler, and the streak over the eye grey: the hind part of the neck transversely striated brown and white: the middle of the back, and scapulars, white, with a very little mixture of brown on the first: wing coverts olive brown, transversely blotched with white; second quills white on the inner webs, on the outer olive brown; (…): tail (…) barred olive brown and white: all the under parts white: bill and legs pale yellow brown. Inhabits Tongataboo. In the collection of Sir Joseph Banks.”

A General Synopsis of Birds. 1790-1801. J. Latham

At that time, the rail from the island of Tongatapu had not yet been given a specific name. Latham, along with the German naturalist Johann Friedrich Gmelin, considered the bird to be a variety of the buff-banded rail (Gallirallus philippensis), a widespread rail species found in many parts of the Pacific. The Scottish ornithologist Robert Gray, around 1850, speculated that the bird from Tongatapu might be a variant of the Lewin’s Rail (Rallus pectoralis).

It wasn’t until 1867 that the naturalist Otto Finsch and ornithologist Gustav Hartlaub challenged these views and recognized the Tongatapu rail as a distinct species, giving it the scientific name Rallus hypoleucus:

“Although there are no further reports on this remarkable rail apart from Latham’s, and it may therefore appear somewhat dubious, we cannot, due to the complete difference in coloration, agree with Gray in considering it a variety of R. pectoralis. Given our limited knowledge of the ornithology of the Tonga Islands, (…) and considering the hidden lifestyle of these birds, it does not seem at all unlikely to us that this characteristic rail may not be found again. Therefore, we do not hesitate to recognize it as a species and to name it specifically.”

Beitrag zur Fauna Centralpolynesiens. Ornithologie der Viti-, Samoa- und Tonga-Inseln. 1867. 163-164. O. Finsch & G. Hartlaub.

Confusion among rails

In the 19th and even the early 20th century, the Tongatapu rail was often confused with other rail species or considered synonymous with them. The British ornithologist Richard Bowdler Sharpe listed Rallus hypoleucus, despite its initial description by Finsch and Hartlaub, as a synonym of Gallirallus philippensis in his Catalogue of the Birds in the British Museum (1894). This decision was likely based on morphological similarities and insufficient information regarding the actual differences between the species.

Similarly, the Australian ornithologist Gregory Mathews, who extensively studied the classification of Australian and Oceanic birds, regarded the Tongatapu rail as a synonym of Rallus forsteri, now known as the buff-banded rail subspecies Gallirallus philippensis ecaudatus.

The confusion among rail species likely stemmed from several factors. These birds often share similar body shapes and plumage characteristics, making differentiation difficult. Additionally, during the time these classifications were made, researchers often had only a few specimens available, and information about variability within and between species was limited. Furthermore, descriptions and illustrations from the 18th and 19th centuries were not always precise, leading to potential oversight or misinterpretation of differences between species.

As a result of these misidentifications, the Tongatapu rail was not recognized as a distinct species for a long time, leading to an underestimation of the biodiversity on the Tonga Islands. The merging of different species under one name also resulted in the loss of valuable information about the specific ecology and distribution of the Tongatapu rail. It wasn’t until 1867 that Finsch and Hartlaub recognized the differences in coloration and morphology of the Tongatapu rail and described it as a valid, distinct species.

The Tongatapu rail in the Baillon Collection?

The Baillon Collection, housed at the Musée George Sand et de la Vallée Noire in La Châtre, France, contains 2,480 preserved specimens of 1,318 bird species, collected by Emmanuel Baillon and his son François Baillon. In a 2014 study, Christophe Gouraud examined 62 bird specimens from this collection, some of which are unidentified and date back to the 18th century.

Among these pre-1800 specimens is one cataloged under the inventory number MLC.2011.0.1170, identified as an indeterminate rail species (Rallidae indet.). This specimen originates from the Tonga Islands, specifically from the main island of Tongatapu, and was donated to the Baillon Collection in 1821 by the naturalist Georges Cuvier. Unfortunately, the specimen is in poor condition, making precise identification very difficult. Due to these preservation issues, it is challenging to determine whether this specimen is the lost Tongatapu rail.

While there are no direct indications that bird specimens from James Cook’s expeditions ended up in the Baillon Collection, it is possible that such specimens could have arrived there indirectly. Specimens originally collected by Joseph Banks and later passed on to other institutions might have eventually made their way into private collections like Baillon’s through sales, trades, or auctions.

The journey of natural history objects is often complex and intricate, particularly in a time when scientific collections were still being established and frequently changed hands. In the Baillon Collection, approximately 400 specimens have lost either their labels or wooden pedestals, resulting in the permanent loss of crucial information about their origins. To definitively determine whether the Tongatapu rail is part of Baillon’s collection, extensive investigations into the provenance and history of the specimens housed there would be necessary.