Christmas imperial pigeon | |
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1887 illustration by Dutch bird illustrator John Gerrard Keulemans | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Columbiformes |
Family: | Columbidae |
Genus: | Ducula |
Species: | D. whartoni |
Binomial name | |
Ducula whartoni (Sharpe, 1887) | |
Synonyms | |
The Christmas imperial pigeon (Ducula whartoni), also known as Black imperial pigeon, Dusky imperial pigeon, Wharton's imperial pigeon, or burong pergam , is a large imperial pigeon endemic to Christmas Island in the northeastern Indian Ocean. It has an overall grey-blue colouration, and juveniles are duller than adults. It makes a soft purring coo sound and a deeper whoo sound comparable to a cow mooing. It lays one glossy white egg per brood, and is possibly somewhat colonial.
Other than the Christmas Island flying fox, the Christmas imperial pigeon is the only fruit-eating (frugivorous) animal on the island, and the pigeon feeds and nests in the dense canopy. It mainly inhabits the tropical inland plateau, and widespread non-native Jamaican cherry forests. It was previously thought to be in danger of extinction due to habitat loss and invasive species (specifically the yellow crazy ant), but it is now considered to be rather common, with a breeding population of about 5,000.
The Christmas imperial pigeon was first described by English ornithologist Richard Bowdler Sharpe in 1887 based on an adult male specimen collected by Captain John Maclear of HMS Challenger. [2] The species name whartoni honours British admiral Sir William Wharton. It is unclear how Sharpe and Wharton are affiliated, but Wharton was made a Fellow of the Royal Society in the previous year, possibly somehow affecting Sharpe's thinking. [3] Sharpe first classified it into the now-defunct genus Carpophaga. In 1933, English zoologist Frederick Nutter Chasen considered the Christmas imperial pigeon to be a subspecies of pink-headed imperial pigeon as D. rosacea whartoni. [4] In 1937, American ornithologist James L. Peters synonymised Carpophaga with Drucula, and disagreed with Chasen, classifying the Christmas imperial pigeon as a distinct species, D. whartoni. [5]
The Christmas imperial pigeon is a species of imperial pigeon (Ducula), which is widely spread out across Oceania, however it is the only imperial pigeon in the Indian Ocean. Likewise, its affinities are unclear. [6] However, the Christmas imperial pigeon could be placed into the D. aenea species complex along with the green (nominate), island, grey, and pink-headed imperial pigeons. The latter is sometimes considered synonymous with the Christmas imperial pigeon. [7]
An adult Christmas imperial pigeon male measures on average 435–470 mm (17.1–18.5 in), and females 440–460 mm (17–18 in). In males, the wing averages 250–264 mm (9.8–10.4 in), and in females 231–258 mm (9.1–10.2 in). The average male weighs 383–700 g (0.84–1.54 lb), and female 406–575 g (0.90–1.27 lb). It is rather large for imperial pigeons, though relatively lightly built. [8]
It has an overall grey-black colour, [9] with darker feathers on the top portion, and lighter feathers on the breast and belly with a burgundy tinge. [10] The beak is black. There is a narrow white band on the base of the upper beak. The eye colour ranges from yellow to orange. The nape and back have a glossy oil-green colour. The wings have glossy bluish-green tips, and are greyish-brown nearer the base. The tail has broad, greenish-brown tips with a somewhat scalloped appearance, and the legs and underside of the tail have reddish-brown feathers. The feet are purple-red. [8]
Juveniles look similar to adults, but have a duller colouration without the oil-green gloss from the lower back to the tail coverts, with a brown breast and belly, a dull grey crown, and grey-brown feet. Eye colour is dark brown. [8]
The Christmas imperial pigeon is known to make a soft gurgling or purring coo sound. It can also make a deep whoo or croo-croo-croo sound which has also been compared to a cow mooing in the distance. It sometimes makes loud clapping sounds with its wings, but in flight, it is largely quiet. [8]
Males have been observed to engage in a courtship display, a "perch coo". A male will slightly puff up its chest, press his bill against it, hold his wings close, and will emit a loud coo before lowering his body to an almost horizontal position. It will rhythmically repeat this motion. [8]
The Christmas imperial pigeon generally constructs nests in the dense forest canopy. One nest was observed to have been 200 mm (7.9 in) in diameter, 60 mm (2.4 in) thick, and constructed using only dead twigs 8 m (26 ft) off the ground in a non-native white leadtree. Peak breeding season may be from November to April. [10] Breeding season is from at least August to April, though predominantly November to March, and the pigeon may be somewhat colonial. It lays a single egg per brood—on rare occasions two—and may lay two broods per year. [8]
One observed chick, probably 10–13 days old, was measured to be 200 mm (7.9 in) long, with developing covert and secondary feathers, and emerging primary feathers. By age 22 days, the chick resembled a small adult, except with remnants of down feathers on the breast and belly, brown feet and irises, and duller plumage. It fledged (became capable of flight) upon reaching 70% of full size at age 24–27 days, and remained dependent on parental care for 17 more days. The chick was fed over a period of 5 to 15 minutes. The chick prodded its parent's throat, and then inserted its beak for about 12 seconds, and did this twice per minutes. Feeding was observed between 9–10 A.M., but probably occurred again in the evening or nighttime. Outside of feeding, it was left alone in the nest, but may have been accompanied through the night. [10]
An egg taken in 1914 was observed to be a broad-elliptical shape, white, slightly glossy, and measured 41.1 mm × 29.8 mm (1.62 in × 1.17 in). [8]
The species is endemic to the tropical 135 km2 (52 sq mi) Christmas Island in the eastern Indian Ocean. [11] [9] It predominantly inhabits the evergreen inland plateau, but is found throughout the island. [9] Though about a third of this was cut down for phosphate mining, the introduced Jamaican cherry trees has recolonized many areas. It was introduced to the Coco Islands (probably Horsburgh Island) sometime between November 1888 and August 1890, with the last sighting made in 1906. [12]
The Christmas imperial pigeon, along with the Christmas Island flying fox, are the only 2 major fruit-eating (frugivorous) animals on the island. As such, the pigeon plays an important role in seed dispersal, seeds swallowed whole and remaining intact [13] (imperial pigeons are able to stretch the base of the jaw to eat larger food items. [6] ) They have been reported feeding on smaller seeded plants such as the stinkwood Celtis timorensis , the common fig, the chinaberry tree, Syzygium nervosum , Tristiropsis acutangula , and the introduced Jamaican cherry. [13] The latter has become a very important food source, [11] with sightings of several hundreds of pigeons where the plant is common. [12]
It generally feeds in flocks in the canopy, isolated trees, or shrubs, and descends to drink from springs or puddles. [12] It has also been observed feeding singly or in pairs. [8] Though frugivorous, the pigeon has been observed repeatedly consuming the leaves of the introduced papaya plant (folivory), which may have been caused by an island-wide shortage of fruit or, less likely, for some therapeutic reason. [14] Peak foraging time appears to be just before dusk. [8]
The Christmas goshawk has been observed preying on a Christmas imperial pigeon chick. [10]
The Christmas imperial pigeon is classified as least concern by the IUCN Red List of Threatened Species and is not protected by the Australian Environment Protection and Biodiversity Conservation Act 1999 because, though its moderately small population is restricted to an island, it appears to be stable with no indication of significant future decline. [1] [9] It is possible that the population fluctuated from the initial settlement of the island in 1888 to the 1970s, with reports of a minor decline. In 1975, ornithologist Gerard Frederick van Tets guessed the total population to be 20 to 200 birds. A 2000 survey estimated the breeding population to be 1,000, and predicted that, due to the rapid spread of the invasive yellow crazy ant, there would be an 80% decline in the pigeon's population over the next 12 years, making it critically endangered. [15] Conversely, a 2003 survey estimated 35,000–66,000 individuals. [12] The International Union for Conservation of Nature (IUCN) lists the population as 5,000 mature individuals, [1] and the pigeon is considered to be common with no major concerns of decline. [9]
Hunting was, historically, the main threat to the Christmas imperial pigeon, and the seeding of Japanese cherry trees along roadsides made it easier game, but the practice was made illegal in 1977. [9] [12]
A 1994 survey found the diet of feral cats consisted predominantly of Christmas imperial pigeon, Christmas Island flying fox, and invasive rats. However, these were more likely scavenged than hunted. [16] [17]
Though there is no quantitative evidence, there are anecdotal reports of yellow crazy ants attacking birds or disturbing nests. Infestations of scale insects, caused by their mutualistic relationship with the ants, has negatively impacted the canopy, and, in the long-term, could lead to decline of the habitat's health. The reduction of the Christmas Island red crab population due to the ants has led to the germination of plants which otherwise would have been eaten by the crabs, which could eventually dramatically alter forest structure. [9]
The yellow crazy ant population is controlled by placing bait laced with the insecticide Fipronil. Surveys from spring 2002 and fall 2003 indicate a reduction in imperial pigeon populations in baited areas, though this may simply be due to seasonal differences in habitation. Nonetheless, ingestion of Fipronil is known to affect feeding behaviour, reproduction, and egg viability in other birds in the long term. [18]
The green imperial pigeon is a large forest pigeon. The large range extends from Nepal, southern India and Sri Lanka eastwards to southern China, Indonesia and the Philippines.
The Nilgiri wood pigeon is large pigeon found in the moist deciduous forests and sholas of the Western Ghats in southwestern India. They are mainly frugivorous and forage in the canopy of dense hill forests. They are best identified in the field by their large size, dark colours and the distinctive checkerboard pattern on their nape.
The nankeen night heron is a heron that belongs to the genus Nycticorax and the family Ardeidae. Due to its distinctive reddish-brown colour, it is also commonly referred to as the rufous night heron. It is primarily nocturnal and is observed in a broad range of habitats, including forests, meadows, shores, reefs, marshes, grasslands, and swamps. The species is 55 to 65 cm in length, with rich cinnamon upperparts and white underparts. The nankeen night heron has a stable population size, and is classified as a species of least concern by the International Union for Conservation of Nature (IUCN).
The elegant imperial pigeon, also known as blue-tailed imperial-pigeon, is a large pigeon, with upperparts mainly dark blue-green in colour with an iridescent sheen. Head, neck and underparts are mostly pale grey, with red-brown undertail coverts.
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.
The mountain imperial pigeon, also known as the maroon-backed imperial pigeon or Hodgson's imperial pigeon, is a species of bird in the pigeon and dove family with a wide range in southeastern Asia.
The Rufescent Imperial Pigeon, also known as the Shining Imperial Pigeon, is a rare species in the world of birds. According to The International Union for Conservative, this species is relatively unknown, and their concern is very minimal. The Union describes that this species is very stable and does not encounter threats from other species The trait of stability is vital in differentiating The Rufescent Imperial Pigeon from the other species confronting threats. This bird in specific does not frequently encounter threats because they are more reserved, quiet birds that tend to remain alone in their habitat. The habitat of these birds allows them to have the frequency of being independent but also gives them the chance to be with other birds. Rooting from the bird family in Columbidae, that also consists of pigeons and doves. In which this family is known for being frugivorous, meaning it primarily feeds on fruit, figs, and seeds.
The white-bellied imperial pigeon is a species of bird in the pigeon family Columbidae. First described by the French ornithologist Charles Lucien Bonaparte in 1854, it is endemic to Indonesia, where it is found on Sulawesi, Buton, Taliabu, Togian, and Peleng. It inhabits primary forest, dense secondary forest, and isolated areas of hill forest. A large pigeon with a long tail, it measures 42.5–51.5 cm (16.7–20.3 in) long and weighs 510 g (18 oz) on average. Males are mainly green, with pale-grey heads and bellies, chestnut vents, and a pale grey tail band, along with a red orbital ring. Females are nearly identical, but have darker grey areas in their plumage.
The barking imperial pigeon, also known as Peale's imperial pigeon, is a species of bird in the pigeon family Columbidae. It is endemic to Fiji, where it occurs on most of the medium and large islands.
The black imperial pigeon, also known as the Bismarck imperial pigeon, is a species of bird in the family Columbidae. It is endemic to the Bismarck Archipelago where it lives in forests.
The Mindoro imperial pigeon, also known as Mindoro Zone-tailed pigeon, Great Mindoro pigeon or Pink-throated Imperial pigeon, is a bird species in the family Columbidae. It is endemic to the mountains of Mindoro in central Philippines and is the largest pigeon in the country reaching 50cm in length.
The Micronesian imperial pigeon, also known as the Micronesian pigeon, and Belochel is a species of bird in the family Columbidae (doves). It is found in Palau, the Caroline Islands, the Marshall Islands and Nauru. Its habitats include montane forests, secondary forests, forests on beaches, and mangroves. It is threatened by hunting and deforestation, and the IUCN has assessed it as a near-threatened species.
The island imperial pigeon is a species of bird in the family Columbidae. It is found in the Bismarck Archipelago and the Solomon Islands archipelago, living in primary and secondary forests and mangroves. The International Union for Conservation of Nature (IUCN) has assessed it as a least-concern species.
The grey-headed imperial pigeon is a species of bird in the family Columbidae. It is endemic to Sulawesi in Indonesia. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests.
The Papuan mountain pigeon is a species of bird in the pigeon family, Columbidae. It is found in the Bacan Islands, New Guinea, the D'Entrecasteaux Islands, and the Bismarck Archipelago, where it inhabits primary forest, montane forest, and lowlands. It is a medium-sized species of pigeon, being 33–36 cm (13–14 in) long and weighing 259 g (9.1 oz) on average. Adult males have slate-grey upperparts, chestnut-maroon throats and bellies, whitish breasts, and a pale grey terminal tail band. The lores and orbital region are bright red. Females are similar, but have grayish breasts and grey edges to the throat feathers.
Mountain pigeons are four species of birds in the genus Gymnophaps in the pigeon family Columbidae. They are found on islands in eastern Indonesia and Melanesia, where they inhabit hill and montane forest. They mostly have dull grey, white, or chestnut-brown plumage, with bright red skin around the eyes being their most distinctive feature. Males and females mostly look alike, but the Papuan mountain pigeon shows slight sexual dimorphism. Mountain pigeons are very social and are usually seen in flocks of at least 10–40 birds, although some species can form flocks of more than 100 individuals. They are generally quiet and do not make many vocalisations. However, they make a distinctive whooshing noise while leaving their high-altitude roosts to feed in the morning.
The pink-necked green pigeon is a species of bird of the pigeon and dove family, Columbidae. It is a common species of Southeast Asia, found from Myanmar and Vietnam south through to the major islands of Indonesia and the Philippines. It is a medium-sized pigeon with predominantly green plumage; only the male has the pink neck that gives the species its name. The species lives in a wide range of forested and human-modified habitats and is particularly found in open habitats. Its diet is dominated by fruit, in particular figs. Pairs lay two eggs in a flimsy twig nest in a tree, shrub, or hedge, and work together to incubate the eggs and raise the chicks. The species is thought to be an important disperser of fruit seeds. The species has adapted well to human changes to the environment, and can be found in crowded cities as long as fruiting trees are present.
The Christmas goshawk or Christmas Island goshawk, is a bird of prey in the goshawk and sparrowhawk family Accipitridae. It is a threatened endemic of Christmas Island, an Australian territory in the eastern Indian Ocean.
The Christmas emerald dove, also known as the Christmas green-winged pigeon, is a bird in the pigeon family, Columbidae. It is a distinctive subspecies of the common emerald dove that is endemic to Christmas Island, an Australian territory in the eastern Indian Ocean.