Spotted green pigeon significant event extinction
Taxonomy
The spotted green pigeon was first mentioned and described by the English ornithologist John Latham in his 1783 work A General Synopsis of Birds. Latham stated that he had seen two specimens, in the collections of the English major Thomas Davies and the naturalist Joseph Banks, but it is uncertain how these ended up in the respective collections, and their provenance is unknown. Though Banks received many specimens from the British explorer James Cook, and Davies received specimens from contacts in New South Wales, implying a location in the South Pacific Ocean, there are no records of spotted green pigeons having been sent from these sources. After Davies' death, his specimen was bought in 1812 by Edward Smith-Stanley, 13th Earl of Derby, who kept it in Knowsley Hall. Smith-Stanley's collection was transferred to the Derby Museum in 1851, where the specimen was prepared from the original posed mount (which had perhaps been taxidermised by Davies himself) into a study skin. This museum later became World Museum, where the specimen is housed today, but Banks' specimen is now lost. Latham also mentioned a drawing of a spotted green pigeon in the collection of the British antiquarian Ashton Lever, but it is unknown which specimen this was based on; it could have been either, or a third individual. Latham included an illustration of the spotted green pigeon in his 1823 work A General History of Birds, and though the basis for his illustration is unknown, it differs from Davies' specimen in some details. It is possible that it was based on the drawing in the Leverian collection, since Latham stated that this drawing showed the end of the tail as "deep ferruginous" (rust-coloured), a feature also depicted in his own illustration.The spotted green pigeon was scientifically named by the German naturalist Johann Friedrich Gmelin in 1789, based on Latham's description. The original binomial name Columba maculata means "spotted pigeon" in Latin. Latham himself accepted this name, and used it in his 1790 work Index ornithologicus. Since Latham appears to have based his 1783 description on Davies' specimen, this can therefore be considered the holotype specimen of the species. Subsequent writers were uncertain about the validity and relationships of the species; the English naturalist James Francis Stephens suggested that it belonged in the fruit pigeon genus Ptilinopus in 1826, and the German ornithologist Johann Georg Wagler instead suggested that it was a juvenile Nicobar pigeon (Caloenas nicobarica) in 1827. The Italian zoologist Tommaso Salvadori listed the bird in an appendix about "doubtful species of pigeons, which have not yet been identified" in 1893. In 1898, the Scottish ornithologist Henry Ogg Forbes supported the validity of the species, after examining Nicobar pigeon specimens and concluding that none resembled the spotted green pigeon at any stage of development. He therefore considered it a distinct species of the same genus as the Nicobar pigeon, Caloenas. In 1901, the British zoologist Walter Rothschild and the German ornithologist Ernst Hartert agreed that the pigeon belonged to Caloenas, but suggested that it was probably an "abnormity", though more than one specimen had been recorded.
The spotted green pigeon was only sporadically mentioned in the literature throughout the 20th century; little new information was published, and the bird remained an enigma. In 2001, the English writer Errol Fuller suggested that the bird had been historically overlooked because Rothschild (an avid collector of rare birds) dismissed it as an aberration, perhaps because he did not own the surviving specimen himself. Fuller considered it a valid, extinct species, and also coined an alternative common name for the bird: the Liverpool pigeon. On the basis of Fuller's endorsement, BirdLife International listed the spotted green pigeon as "Extinct" on the IUCN Red List in 2008; it was previously "Not Recognized". In 2001, the British ornithologist David Gibbs stated that the spotted green pigeon was only superficially similar to the Nicobar pigeon, and possibly distinct enough to warrant its own genus (related to Ptilinopus, Ducula, or Gymnophaps). He also hypothesised that the bird might have inhabited a Pacific island, based on stories told by Tahitian islanders to the Tahitian scholar Teuira Henry in 1928 about a green and white speckled bird called titi. The American palaeontologist David Steadman disputed the latter claim in a book review, noting that titi is an onomatopoeic word (resembling the sound of the bird) used especially for shearwaters (members of Procellariidae) in east Polynesia. The English ornithologists Julian P. Hume and Michael Walters, writing in 2012, agreed with Gibbs that the bird warranted generic status.In 2020, after examining historical texts to clarify the origin and extinction date of the spotted green pigeon, the French ornithologist Philippe Raust pointed out that the information in Henry's 1928 book Ancient Tahiti was not gathered by her, but by her grandfather, the English reverend John Muggridge Orsmond, who collected ancient Tahitian traditions during the first half of the 19th century. The book devotes several pages to birds of Tahiti and its surroundings, including extinct ones, and the entry that Gibbs had linked to the spotted green pigeon reads: "The titi, which cried “titi”, now extinct in Tahiti, was speckled green and white and it was the shadow of the mountain gods". The titi was included in the paragraph relating to pigeons, which suggests it was well recognised as such, and Raust found it consistent with the spotted green pigeon. Though Steadman had dismissed the idea based on the name titi also being used for shearwaters, Raust pointed out that this name was used for a wider variety of birds with vocalisations that sound like "titi". Raust also noted that an 1851 Tahitian dictionary compiled by the Welsh reverend John Davies included the word tītīhope’ore, which was used as a synonym for the titi of Henry in a 1999 dictionary. Based on definitions in Davies' dictionary, Raust translated this name as "tītī without (a long) tail." Raust suggested this name was used to distinguish it from the long-tailed koel (Urodynamis taitensis), which is called "tītī oroveo", and which is somewhat similar to Latham's illustration of the spotted green pigeon, being dark brown with paler spots and underparts. Raust believed that the study of these texts reinforced the Tahitian origin of the spotted green pigeon, and suggested this could be confirmed if possible bones of this species were one day found on Tahiti and analysed for DNA. So far, few paleontological sites on Tahiti have been studied, and fossils found there have not yet revealed unknown species.The only specimen is today catalogued as WML 3538 at  World Museum, Liverpool, where it is locked under environmentally-controlled conditions outside public view. It is kept in a cabinet in the museum's basement with other particularly important bird specimens, such as other extinct birds and type specimens. The store room is monitored for pests, and the temperature and humidity is kept stable to avoid infestations and damp. The specimen is handled with gloves when examined by researchers, and exposure to light is limited.