Ducula is a genus of the pigeon family Columbidae, collectively known as imperial pigeons. They are large to very large pigeons with a heavy build and medium to long tails. They are arboreal, feed mainly on fruit and are closely related to the other genus of fruit-eating doves, Ptilinopus. Both genera display brightly coloured plumage, predominantly green, often with contrasting under-parts of purple, orange or red. Some Ducula have prominently swollen ceres. They have large gapes and swallow seeds whole, playing an important role in seed dispersal.
Imperial pigeons are found in forests of southern Asia, New Guinea, northern Australia and the Pacific islands. Many species are nomadic, travelling long distances to exploit seasonal fruit sources. Some undertake migrations and all are strong fliers. Because of habitat loss and predation, species of Ducula are amongst the most threatened of avian species globally.
Taxonomy The genus Ducula was introduced in 1836 by the English naturalist Brian Houghton Hodgson with Ducula insignis as the type species. This taxon is now considered as a subspecies of the mountain imperial pigeon (Ducula badia). The genus name Ducula is from the Latin dux genitive ducis meaning "leader".
The taxonomy of the imperial pigeon is unresolved, with the number of species within the genus Ducula reported variably as 34 and 36. Derek Goodwin's 1959 paper on the taxonomy of the genus Ducula divides his arrangement of 36 species into 7 subgroups according to distribution and phenotype, and this classification is followed by Gibbs et al. The current (2024) version of the IOC World Bird List includes 42 extant species and this is followed here.
Species The genus contains 42 species: Section Image Scientific name Distribution Poliocephala species-group Ducula poliocephala pink-bellied imperial pigeon Philippines. Ducula forsteni white-bellied imperial pigeon Indonesia (Sulawesi, Buton, Taliabu, Togian, and Peleng.) Ducula mindorensis Mindoro imperial pigeon Philippines (Mindoro)Ducula radiata Grey-headed imperial pigeon Indonesia (Sulawesi) Carola species-group Ducula carola Spotted imperial pigeon Philippines Aenea species-group Ducula aenea Green imperial pigeon Nepal, southern India and Sri Lanka eastwards to southern China, Indonesia and the Philippines. Ducula oenothorax Enggano imperial pigeon Enggano Island. Ducula nicobarica Nicobar imperial pigeon Nicobar Islands. Ducula perspicillata Spectacled imperial pigeon Maluku Islands. Ducula neglecta Seram imperial pigeon Moluccas Ducula concinna Elegant imperial pigeon New Guinea, Talaud Islands, Sangihe, islands off southern Sulawesi, the southern Maluku Islands, and the eastern Lesser Sundas from Romang to Tanimbar, east up to the Aru Islands. Ducula pacifica Pacific imperial pigeon American Samoa, the Cook Islands, Fiji, Kiribati, Niue, Papua New Guinea, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, Vanuatu, and Wallis and Futuna Islands. Ducula oceanica Micronesian imperial pigeon Palau, the Caroline Islands, the Marshall Islands and Nauru. Ducula aurorae Polynesian imperial pigeon French Polynesia. Ducula galeata Marquesan imperial pigeon Nuku Hiva in the Marquesas Islands of French Polynesia. Ducula rubricera Red-knobbed imperial pigeon Bismarck Archipelago and the Solomon Islands archipelago.Ducula myristicivora Spice imperial pigeon Indonesia Ducula geelvinkiana Geelvink imperial pigeon Indonesia's Schouten Islands Ducula rufigaster Purple-tailed imperial pigeon New Guinea. Ducula basilica Cinnamon-bellied imperial pigeon Moluccas. Ducula finschii Finsch's imperial pigeon Papua New Guinea. Ducula chalconota Rufescent imperial pigeon New Guinea. Ducula pistrinaria Island imperial pigeon Bismarck Archipelago and the Solomon Islands archipelago Ducula rosacea Pink-headed imperial pigeon Lesser Sunda Islands of Indonesia Ducula whartoni Christmas imperial pigeon Christmas Island Ducula pickeringii Grey imperial pigeon Sulu Archipelago, Miangas and Talaud Islands Ducula latrans Barking imperial pigeon FijiBrenchleyi species-group Ducula brenchleyi Chestnut-bellied imperial pigeon Solomon Islands. Ducula bakeri Vanuatu imperial pigeon Vanuatu Ducula goliath Goliath imperial pigeon New Caledonia. Ducula pinon Pinon's imperial pigeon New Guinea. Ducula melanochroa Black imperial pigeon Bismarck Archipelago Ducula mullerii Collared imperial pigeon New GuineaZoe's imperial pigeon Ducula zoeae Zoe's imperial pigeon New Guinea. Badia species group Ducula cuprea Malabar imperial pigeonWestern Ghats of India. Ducula badia Mountain imperial pigeon Bangladesh, Bhutan, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand, and Vietnam Ducula lacernulata Dark-backed imperial pigeon Lesser Sunda Islands. Ducula cineracea Timor imperial pigeon Timor and Wetar. Bicolor species-group Ducula bicolor Pied imperial pigeon Myanmar and Thailand, throughout Indonesia and east to the Philippines and the Bird's Head Peninsula in New Guinea. Ducula luctuosa Silver-tipped imperial pigeon Sulawesi Ducula spilorrhoa Torresian imperial pigeon Australia (north-east Western Australia, north Northern Territory and north Queensland, including the Torres Strait Islands), New Guinea, Aru Islands, islands in the Geelvink Bay, D'Entrecasteaux Islands and Louisiade Archipelago. Ducula subflavescens Yellowish imperial pigeon Bismarck Archipelago.
Two recently extinct species have also been described from archaeological remains: Ducula tihonireasini from the Gambier Islands, French Polynesia Shutler's fruit pigeon (Ducula shutleri) from Tonga
Description
Poliocephala species-group
Four species of imperial pigeon are found in Philippines and Sulawesi. All have a distinct pale band across the centre of the tail, and a rich green or purple dorsum. This grouping shares characteristics and distribution with Ptilinopus, and forms a link between the genera. The pink-belled (D. poliocephala) and the white-bellied (D. forsteni) imperial pigeon are similar and allopatric species. The Mindoro (D. mindorensis) and the grey-headed (D. radiata) imperial pigeons differ in size but are otherwise similar.
Carola species-group
The spotted imperial pigeon (D. carola) is sympatric to D. poliocephala, and though smaller, short tailed and with spotted plumage, it is similar enough in appearance and distribution to suggest the taxa are related.
Aenea species-group
This group's nominate species is the green imperial pigeon (D. aenea), distinctive by its iridescent green, purple or bronze upper-parts and wings. The species-group is widespread through the Asia-Pacific. It is further separated into subgroups by Goodwin.
Three Asian species with iridescent green upper-parts, pink head and neck with normal sized ceres; D. aenea, the elegant (D. concinna) and the white-eyed or spectacled (D. perspicillata) imperial pigeons. The pacifica subgroup of six species, similar to aenea but with enlarged ceres, and distributed throughout the Pacific. The Pacific (D. pacifica) and the Micronesian (D. oceania) imperial pigeons are similar allospecies, while the Polynesian (D. aurorae) and Marquesan (D. galeata) imperial pigeons are larger birds with dark plumage. The red-knobbed imperial pigeon (D. rubricera) and the spice imperial pigeon (D. myristicivora) are similar but found in Melanesia and New Guinea. The finschii subgroup of four species which may be New Guinea representatives of D. aenea stock; the purple-tailed (D. rufigaster), cinnamon-bellied (D. basilica) and Finsch's imperial pigeons, which all inhabit offshore islands. The shining or rufescent imperial pigeon (D. chalconota) occupies more elevated ranges on the New Guinea mainland. Another subgroup similar to aenea, but with upper parts not iridescent and less well defined, is the pink-headed imperial pigeon (D. rosacea) as the nominate species, the Christmas Island (D. whartoni), the grey (D. pickeringii) and the island (D. pistrinaria) imperial pigeons.
Brenchleyi species-group
Contains 4 subgroups of large dark chestnut-bellied pigeons.
The chestnut-bellied imperial pigeon (D. brenchleyi) is the nominate species with the Baker's (D. bakeri), Peale's (D. latrans), and New Caledonian (D. goliath) imperial pigeons, being allopatric through the Western Pacific islands. The Pinon imperial pigeon (D. pinon) is found in New Guinea and its islands. The collared imperial pigeon (D. mullerii) is found in New Guinea and Aru and has a distinctive dark collar. The Bismarck imperial pigeon (D. melanochroa) is found on the Bismarck Archipelago.
Zoe's imperial pigeon
D. zoeae of Indonesia and New Guinea, is sufficiently distinct in colour to be placed in a species-group of its own.
Badia species group
The mountain (D. badia) and the dark-backed (D. lacernulata) imperial pigeons have a widespread distribution, the former from Indian subcontinent to south China and Malaysia, and the latter in southern Indonesia. The Timor imperial pigeon (D. cineracea) is a similar grey pigeon, but found in Timor.
Bicolor species-group
The pied imperial pigeons form a discrete group of large white pigeons with black wingtips, found in New Guinea and its islands, and northern Australia. Goodwin recognised three species; the pied (D. bicolor) the white (D. luctuosa) and the Torresian (D. spilorrhoa). The three allopatric species are closely related and subsequent authors have challenged this ranking, Johnstone including all three in a single species. Gibbs et al. group D. bicolor and D. spilorrhoa together, but adds the yellow-tinted imperial pigeon (D. subflavescens) as another species. Frith includes D. subflavescens as a race of D. spilorrhoa. Sibley and Monroe (1990) follow Goodwin.
The difficulty in assigning or removing species rank is compounded by the lack of data on behaviour and breeding patterns of the taxa. Similar species are allopatric, and there is no data on whether the species freely interbreed or not. Data on voice and behaviour is similarly poor.
The confusion is not helped by English naming. D. bicolor is variously described as the nutmeg pigeon, the Torres Strait pigeon, and the pied imperial pigeon. D. spilorrhoa is also described as the nutmeg pigeon, the white nutmeg pigeon, the Australian pied pigeon, the Australian pied imperial pigeon, the Torres Strait pigeon or the Torresian imperial pigeon.
Distribution and habitat
Imperial pigeons are only found in southern Asia, Australia, New Guinea and the Pacific, a distribution from the Himalayas (D. badia) to Tahiti in the South Pacific (D. aurorare). The greatest diversity of birds is in New Guinea. Imperial pigeons are strong fliers, are capable of flight over oceans, and have been successful in colonising islands and archipelagos.
Australia has a poor representation of Ducula amongst its fauna, with only one species breeding on the mainland (D. spilorrhoa). There is no clear explanation why more species of Ducula did not cross the Torres Strait islands to reach mainland Australia. The genus Lopholaimus, comprising only one species may have been well represented on the Australian mainland before European settlement, thus excluding Ducula.
Imperial pigeons are arboreal, and found almost exclusively in forest and woodland habitats where there is availability of fruit bearing trees. About half of the species occupy mountainous forest to elevations of 2500m. Many are found on islands, and live in coastal forests, with a few species inhabiting forest edges or mangroves.
Appearance