Silvery Pigeon
Encyclopedia
The Silvery Pigeon also known as Silvery Wood-pigeon or Grey Wood-pigeon is a species
of pigeon found in Indonesia and Malaysia. It was thought to be extinct but wild populations were rediscovered in 2008 near Masokut Island might represent this species.
Most distinguishing characteristics are located on the head, which is shaped differently, with a sloping forehead (rounded in the PIP), conspicuous dark red or purplish eye-wattles (none in the PIP) and eyes, and a bill that is darker at the base (lighter at the base in the PIP), being dusky purple with a pale apple-green tip. The feet are bluish-grey, mottled with varying amounts of red. The birds are slightly smaller than the PIP, with a total length of around 37 cm, females being marginally larger and darker than males on average, and juvenile birds are apparently more sandy-coloured on the upperpart feather fringes and breast. While the weight is not recorded, comparison with related species gives an estimate of 350 grams on average.
The colour pattern, unusual for a Columba pigeon, probably represents convergent evolution
towards the PIP, and possibly even a case of Müllerian mimicry, the anti-predator attribute being the PIP's habit to aggregate in large flocks which makes it harder for predators to pick out individual birds, and enables the much rarer Silvery Pigeon to share this advantage.
) and west of Sumatra
, Indonesia
, and on the adjacent mainland. The oldest record is that of a specimen supposedly taken near Pontianak
before 1850. Verifiable records exist from Burong Island, Sarawak (1899), Saya in the Lingga Islands
(same year), Simeulue
(e.g. Teluk Dalam and Teluk Labuan Bajau, 1901), South Pagai
(1902) and Sipura
in the Mentawai Islands
, the Riau Islands (several times), Tuangku Airdingin (1913), Jemaja Andriabu in the Anamba Islands (1925), the North Natuna Islands
(1928), and in Sumatra's Jambi and possibly South Sumatra
provinces. Locations recorded earlier included Bintan
in the Riau Islands (June 1930) and Pulau Gurungan Besar in the Karimata islands
(March 1931) and (unconfirmed, before 1937) from Pulau Jarak in the Straits of Malacca. The species was rediscovered in the wild only in 2010 from the Talang Islands.
forests and other woodland in the low-lying offshore islands and adjacent coastal regions, at an altitude below 100 m ASL
. It is believed to wander around following fruit in season, and was often found in association with much larger flocks of the Pied Imperial Pigeon. It also breeds in these birds' nesting colonies, probably over a period of several months from March/April on. Like most other pigeons, it builds a flimsy stick nest in trees and lays a single white egg, which has a chalky, not glossy shell (as opposed to that of the PIP).
, translating into an estimated population of less than fifty mature individuals. This is based on a lack of confirmed sightings, however, and thus the species may actually be more common and simply not identified. Following the rule-of-thumb "no confirmed sightings for 50 years", the species could theoretically be considered extinct, but using the precautionary principle
, it is instead classified as critically endangered
because it is under most conditions not identifiable with any certainty in the field and although no recent verified records exists, there are some promising recent reports.
The reasons for the bird's apparent decline are not well known. While deforestation, especially the removal of mangrove forests, certainly adversely affects this bird, it is not known to have started on a massive scale at such an early date. Similarly, introduction of alien predators (like cats that become feral) will jeopardize breeding on offshore islets, but this is also not believed to have been significant at the time the records ceased. At any rate, the species is not found anymore on Burong, Simeulue, the Mentawi and the Riau Islands today.
There are some 1980s and 1990s records, supposedly of large numbers of individuals, from Padang-Sugihan Wildlife Reserve and Sembilang River in South Sumatra, and Berbak National Park
in Jambi province. It is conjectured that the bird may exist, possibly in considerable numbers, in South Sumatra, especially the Banyuasin peninsula, or Padang-Sugihan Wildlife Reserve. None of these records has been verified, however, and the species was never considered to be particularly numerous, especially when compared to the PIP. Most recently, the Silvery Pigeon was believed to have been seen on Pulau Talang Besar, Talang Talang Islands (part of Talang-Satang National Park), in 2001 (Wilson, 2004). Butchart et al. (2006) also mention an unconfirmed record in 2002.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of pigeon found in Indonesia and Malaysia. It was thought to be extinct but wild populations were rediscovered in 2008 near Masokut Island might represent this species.
Description
The Silvery Pigeon is not distinguishable from the Pied Imperial Pigeon at a distance, although this is not necessarily true vice-versa; as the Pied Imperial Pigeon can vary between a pale grey, pure white and even yellowish colouration, it is often possible to tell that a bird is not a C. argentina. At close quarters, the Silvery Pigeon may be recognized by a few characteristics: The plumage is always a pale silvery grey, with black remiges and ends of the tail feathers; there may be a slight greenish sheen on the feathers of the backsides of the neck. The black part of the tail is equal in length in all feathers, whereas it forms a black triangle pointing headwards on the underside of the Pied Imperial Pigeon's tail.Most distinguishing characteristics are located on the head, which is shaped differently, with a sloping forehead (rounded in the PIP), conspicuous dark red or purplish eye-wattles (none in the PIP) and eyes, and a bill that is darker at the base (lighter at the base in the PIP), being dusky purple with a pale apple-green tip. The feet are bluish-grey, mottled with varying amounts of red. The birds are slightly smaller than the PIP, with a total length of around 37 cm, females being marginally larger and darker than males on average, and juvenile birds are apparently more sandy-coloured on the upperpart feather fringes and breast. While the weight is not recorded, comparison with related species gives an estimate of 350 grams on average.
The colour pattern, unusual for a Columba pigeon, probably represents convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
towards the PIP, and possibly even a case of Müllerian mimicry, the anti-predator attribute being the PIP's habit to aggregate in large flocks which makes it harder for predators to pick out individual birds, and enables the much rarer Silvery Pigeon to share this advantage.
Distribution
This species was recorded during the late 19th and early 20th century from offshore islands of the Natuna Sea (west of BorneoBorneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
) and west of Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, and on the adjacent mainland. The oldest record is that of a specimen supposedly taken near Pontianak
Pontianak, Indonesia
Pontianak is the capital of the Indonesian province of West Kalimantan. It is a medium-size industrial city on the island of Borneo. Pontianak occupies an area of 107.82 km² in the delta of the Kapuas River...
before 1850. Verifiable records exist from Burong Island, Sarawak (1899), Saya in the Lingga Islands
Lingga Islands
Not to be confused with "Linga", a common Scottish island name, see Linga The Lingga Islands or Lingga Archipelago are a group of islands in Indonesia, located south of Singapore, along both sides of the equator, off the eastern coast of Riau Islands province on Sumatra island...
(same year), Simeulue
Simeulue
Simeulue Regency is a regency in the Aceh province of Indonesia. It occupies the whole island of Simeulue , 150 km off the west coast of Sumatra, with a population of 80,279 ....
(e.g. Teluk Dalam and Teluk Labuan Bajau, 1901), South Pagai
South Pagai
South Pagai is one of the Mentawai Islands off the west coast of Sumatra in Indonesia. It is south of North Pagai Island...
(1902) and Sipura
Sipura
Sipura, or Sipora located off Sumatra in Indonesia, is the smallest and most developed of the four Mentawai Islands at only 845 km². The regency capital of the Mentawai Islands, Tua Pejat, is found on Sipora. An estimated 10-15% of the original rainforest remains on this island.Sipora is a...
in the Mentawai Islands
Mentawai Islands
The Mentawai Islands are a chain of about seventy islands and islets off the western coast of Sumatra in Indonesia. Siberut is the largest of the islands. The other major islands are Sipura, North Pagai and South Pagai . The islands lie approximately 150 km off the Sumatran coast, across the...
, the Riau Islands (several times), Tuangku Airdingin (1913), Jemaja Andriabu in the Anamba Islands (1925), the North Natuna Islands
Natuna Islands
The Natuna Islands archipelago is located in the Natuna Sea in the larger Tudjuh Archipelago, off the northwest coast of Borneo. The islands are administratively part of the Riau Islands province of Indonesia and are the northernmost non-disputed island group of Indonesia...
(1928), and in Sumatra's Jambi and possibly South Sumatra
South Sumatra
South Sumatra is a province of Indonesia.-Geography:It is on the island of Sumatra, and borders the provinces of Lampung to the south, Bengkulu to the west, and Jambi to the north...
provinces. Locations recorded earlier included Bintan
Bintan
Bintan Island or Negeri Segantang Lada is an island in the Riau archipelago of Indonesia. It is part of the Riau Islands province, the capital of which, Tanjung Pinang, lies in the island's south and is the island's main community....
in the Riau Islands (June 1930) and Pulau Gurungan Besar in the Karimata islands
Karimata islands
The Karimata Islands are a chain of small islands off the west coast of Indonesian Borneo, the largest of which is Karimata, being about 20 km across , and situated at...
(March 1931) and (unconfirmed, before 1937) from Pulau Jarak in the Straits of Malacca. The species was rediscovered in the wild only in 2010 from the Talang Islands.
Ecology
The Silvery Pigeon is known from mangroveMangrove
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...
forests and other woodland in the low-lying offshore islands and adjacent coastal regions, at an altitude below 100 m ASL
Above mean sea level
The term above mean sea level refers to the elevation or altitude of any object, relative to the average sea level datum. AMSL is used extensively in radio by engineers to determine the coverage area a station will be able to reach...
. It is believed to wander around following fruit in season, and was often found in association with much larger flocks of the Pied Imperial Pigeon. It also breeds in these birds' nesting colonies, probably over a period of several months from March/April on. Like most other pigeons, it builds a flimsy stick nest in trees and lays a single white egg, which has a chalky, not glossy shell (as opposed to that of the PIP).
Current status
This species has been classified as Critically Endangered (D1) by BirdLife InternationalBirdLife 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...
, translating into an estimated population of less than fifty mature individuals. This is based on a lack of confirmed sightings, however, and thus the species may actually be more common and simply not identified. Following the rule-of-thumb "no confirmed sightings for 50 years", the species could theoretically be considered extinct, but using the precautionary principle
Precautionary principle
The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those...
, it is instead classified as critically endangered
Critically endangered
Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...
because it is under most conditions not identifiable with any certainty in the field and although no recent verified records exists, there are some promising recent reports.
The reasons for the bird's apparent decline are not well known. While deforestation, especially the removal of mangrove forests, certainly adversely affects this bird, it is not known to have started on a massive scale at such an early date. Similarly, introduction of alien predators (like cats that become feral) will jeopardize breeding on offshore islets, but this is also not believed to have been significant at the time the records ceased. At any rate, the species is not found anymore on Burong, Simeulue, the Mentawi and the Riau Islands today.
There are some 1980s and 1990s records, supposedly of large numbers of individuals, from Padang-Sugihan Wildlife Reserve and Sembilang River in South Sumatra, and Berbak National Park
Berbak National Park
The Berbak National Park in Sumatra island, Jambi province of Indonesia, forms part of the largest undisturbed swamp forest in southeastern Asia, and the peat swamp forest with the greatest number of palm species...
in Jambi province. It is conjectured that the bird may exist, possibly in considerable numbers, in South Sumatra, especially the Banyuasin peninsula, or Padang-Sugihan Wildlife Reserve. None of these records has been verified, however, and the species was never considered to be particularly numerous, especially when compared to the PIP. Most recently, the Silvery Pigeon was believed to have been seen on Pulau Talang Besar, Talang Talang Islands (part of Talang-Satang National Park), in 2001 (Wilson, 2004). Butchart et al. (2006) also mention an unconfirmed record in 2002.