Torresian Imperial-pigeon
Encyclopedia
The Torresian Imperial Pigeon (Ducula spilorrhoa), also known as the Nutmeg Pigeon or Torres Strait Pigeon, is a relatively large, pied species of pigeon. It is found in forest, woodland, savanna, mangrove and scrub in 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
. It has also been recorded as a vagrant in New South Wales
, Australia. As far as known, most populations are resident or only take part in minor local movements, but the population in Queensland leaves for New Guinea in February–April and returns in July–August.
The Torresian Imperial Pigeon is a large plump pigeon, 38-44 centimetre
s (15-17.5 inch
es) in length, and with a 45 cm (18 in) wingspan. It is entirely white or pale cream
, apart from the black flight feathers (remiges), part of the tail (rectrices) and spots on the undertail coverts
. The head can be brown, soiled by eating fruit.
of the pigeon is fast and direct, with the regular beats and an occasional sharp flick of the wing
s which are characteristic of pigeons in general.
in a tree, usually a coconut palm
and lays a single white egg, which hatches within 26 to 28 days. The squab fledges after another three weeks. In Australia they breed between August and January in mangrove
s, vine
s, palm
fronds on off-shore islands, such as the Brook Islands
. In north-east Queensland, they migrate daily as flocks from the islands to the mainland rainforest
s to eat fruit
, returning to the islands at dusk.
. It can swallow fruits with very large seeds, the latter being regurgitated
or excreted
whole, depending on size, after the pulp has been removed.
Its taxonomy
is confusing and remains unsettled. It has sometimes been considered a subspecies
of the Pied Imperial Pigeon. When recognized as a separate species, the number of subspecies of the Torresian Imperial Pigeon also remains unsettled. Many recognize two: The widespread D. s. spilorrhoa (nominate) and D. s. constans of the Kimberleys. However, the latter is sometimes considered a junior synonym of former. Alternatively, it has been argued that it should be considered a separate species, the Kimberley Imperial-pigeon (D. constans Bruce, 1989). Two additional taxa, subflavescens of the Bismarck Archipelago
and melanura of the Moluccas, have been associated with the Torresian Imperial Pigeon. The former has a distinctive yellowish-tinged plumage
and a bluish basal half of the bill, and is increasingly treated as a separate species, the Yellowish Imperial-pigeon
(D. subflavescens). Most recent authorities place melanura under the Pied Imperial Pigeon, but it has black spotting to the undertail coverts and a greenish-yellow bill similar to the Torresian Imperial Pigeon. However, melanura also has a significantly broader black tail-tip than the Torresian Imperial Pigeon.
s. It was described by Harold Frith
in 1982, who stated these processions as "one of the great ornithological experiences of the tropics." However, the birds were subject to mass slaughter in the 19th and early 20th Centuries because they were thought of as pests or easy targets for recreational shooting. Populations dropped rapidly before conservation activists such as Margaret and Arthur Thorsborne
led a campaign to protect them and monitor their numbers.
The population is now slowly increasing because of their protected status in Australia, where there are now an estimated 30,000. The species remains locally fairly common in parts of its range, and is therefore considered to be of least concern
by BirdLife International
and IUCN.
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
(north-east Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
, north Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
and north Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, including the Torres Strait Islands
Torres Strait Islands
The Torres Strait Islands are a group of at least 274 small islands which lie in Torres Strait, the waterway separating far northern continental Australia's Cape York Peninsula and the island of New Guinea but Torres Strait Island known and Recognize as Nyumaria.The islands are mostly part of...
), New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, Aru Islands
Aru Islands
The Aru Islands are a group of about ninety-five low-lying islands in the Maluku province of eastern Indonesia. They also form a regency of Indonesia.-Geography:...
, islands in the Geelvink Bay, D'Entrecasteaux Islands
D'Entrecasteaux Islands
D'Entrecasteaux Islands are situated near the eastern tip of New Guinea in the Solomon Sea in Milne Bay Province of Papua New Guinea. The group spans a distance of 160 km, has a total land area of approximately 3,100 km² and is separated from the Papua New Guinea mainland by the...
and Louisiade Archipelago
Louisiade Archipelago
The Louisiade Archipelago is a string of ten larger volcanic islands frequently fringed by coral reefs, and 90 smaller coral islands located 200 km southeast of New Guinea, stretching over more than and spread over an ocean area of between the Solomon Sea to the north and the Coral Sea to...
. It has also been recorded as a vagrant in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia. As far as known, most populations are resident or only take part in minor local movements, but the population in Queensland leaves for New Guinea in February–April and returns in July–August.
Description
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
s (15-17.5 inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
es) in length, and with a 45 cm (18 in) wingspan. It is entirely white or pale cream
Cream (colour)
Cream is the colour of the cream produced by cattle grazing on natural pasture with plants rich in yellow carotenoid pigments, some of which are incorporated into the cream, to give a yellow tone to white. Cream is the pastel colour of yellow, much like as pink is to red. Cream is used as a skin...
, apart from the black flight feathers (remiges), part of the tail (rectrices) and spots on the undertail coverts
Covert (feather)
A covert feather on a bird is one of a set of feathers, called coverts, which as the name implies, cover other feathers. The coverts help to smooth airflow over the wings and tail.- Wing-coverts :...
. The head can be brown, soiled by eating fruit.
Behaviour
The flightFlight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....
of the pigeon is fast and direct, with the regular beats and an occasional sharp flick of the wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
s which are characteristic of pigeons in general.
Breeding
The male displays by flying up steeply, pausing, tipping forward and then gliding downwards. It builds an untidy stick nestBird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
in a tree, usually a coconut palm
Coconut
The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...
and lays a single white egg, which hatches within 26 to 28 days. The squab fledges after another three weeks. In Australia they breed between August and January in mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s, vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...
s, palm
Arecaceae
Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...
fronds on off-shore islands, such as the Brook Islands
Brook Islands National Park
The Brook Islands National Park is a national park in Queensland, Australia, 1246 km northwest of Brisbane, with an area of 0.9 km². It was established in 1994 and comprises three islands - North, Tween and Middle - which lie off the coast 7 km north-east of Cape Richards on Hinchinbrook Island...
. In north-east Queensland, they migrate daily as flocks from the islands to the mainland rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
s to eat fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
, returning to the islands at dusk.
Feeding
This is an arboreal dove, feeding almost exclusively on fruitFruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
. It can swallow fruits with very large seeds, the latter being regurgitated
Regurgitation (digestion)
Regurgitation is the expulsion of material from the mouth, pharynx, or esophagus, usually characterized by the presence of undigested food or blood.Regurgitation is used by a number of species to feed their young...
or excreted
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...
whole, depending on size, after the pulp has been removed.
Taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
is confusing and remains unsettled. It has sometimes been considered a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Pied Imperial Pigeon. When recognized as a separate species, the number of subspecies of the Torresian Imperial Pigeon also remains unsettled. Many recognize two: The widespread D. s. spilorrhoa (nominate) and D. s. constans of the Kimberleys. However, the latter is sometimes considered a junior synonym of former. Alternatively, it has been argued that it should be considered a separate species, the Kimberley Imperial-pigeon (D. constans Bruce, 1989). Two additional taxa, subflavescens of the Bismarck Archipelago
Bismarck Archipelago
The Bismarck Archipelago is a group of islands off the northeastern coast of New Guinea in the western Pacific Ocean and is part of the Islands Region of Papua New Guinea.-History:...
and melanura of the Moluccas, have been associated with the Torresian Imperial Pigeon. The former has a distinctive yellowish-tinged plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
and a bluish basal half of the bill, and is increasingly treated as a separate species, the Yellowish Imperial-pigeon
Yellowish Imperial-pigeon
The Yellowish Imperial Pigeon , also known as the Yellow-tinted Imperial Pigeon or Bismarck Imperial Pigeon , is a relatively large species of bird in the Columbidae family. It is endemic to forest and woodland in the Bismarck Archipelago...
(D. subflavescens). Most recent authorities place melanura under the Pied Imperial Pigeon, but it has black spotting to the undertail coverts and a greenish-yellow bill similar to the Torresian Imperial Pigeon. However, melanura also has a significantly broader black tail-tip than the Torresian Imperial Pigeon.
Status
The birds were once present in large colonies in Cairns, Australia. Edmund Banfield wrote in 1908 that in Dunk Island "fully 100,000 come and go evening and morning", with flying colonies as wide as two mileMile
A mile is a unit of length, most commonly 5,280 feet . The mile of 5,280 feet is sometimes called the statute mile or land mile to distinguish it from the nautical mile...
s. It was described by Harold Frith
Harold James Frith
Harold James Frith AO was an Australian administrator and ornithologist. He was born at Kyogle, New South Wales and studied Agricultural Science at Sydney University. He first joined the CSIRO Division of Plant Industry but later transferred to the Division of Wildlife and carried out extensive...
in 1982, who stated these processions as "one of the great ornithological experiences of the tropics." However, the birds were subject to mass slaughter in the 19th and early 20th Centuries because they were thought of as pests or easy targets for recreational shooting. Populations dropped rapidly before conservation activists such as Margaret and Arthur Thorsborne
Margaret Thorsborne
Margaret Grace Thorsborne AO is an Australian naturalist, conservationist and environmental activist. She is notable for her efforts, with her husband Arthur Thorsborne, in initiating the long-term monitoring and protection of the Torresian Imperial-pigeon on the Brook Islands, north east of...
led a campaign to protect them and monitor their numbers.
The population is now slowly increasing because of their protected status in Australia, where there are now an estimated 30,000. The species remains locally fairly common in parts of its range, and is therefore considered to be of least concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
by BirdLife International
BirdLife International
BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...
and IUCN.