Socorro Dove
Encyclopedia
The Socorro Dove is a dove
that is extinct in the wild
. It was endemic
to Socorro Island
in the Revillagigedo Islands
off the west coast of Mexico. The last sighting in its natural habitat was in 1972
. There are not more than 200 and probably fewer than 100 purebred birds in captivity. A reintroduction programme is in the early stages of preparation.
It is a close relative of the Mourning
and Eared Dove
s, particularly the former and was at one time considered its subspecies
. In captivity, it hybridizes vigorously with the former and almost all privately-owned birds as well as several of the captive breeding programmes that lack a pedigree are known or strongly suspected to be such hybrids. They are excluded from the reintroduction program as there is evidence of unique adaptation
s in the Socorro species. The scientific name commemorates Zénaïde Laetitia Julie Bonaparte
and the American ornithologist and artist Andrew Jackson Grayson
.
. It is 26.5–34 cm long and weighs 190 g on average. In overall color pattern, it agrees with its relatives. It is considered to be a stronger-colored insular representative of the Mourning Dove
. The male is deep cinnamon on its head and underparts, with an ear streak like its relatives. The nape
is blue-grey and the neck has an iridescent pink patch, most prominent after moult
. The upperparts are rufous brown. Female and juvenile coloration is slightly duller. The most conspicuous differences from the Mourning Dove - darker coloration and more well-developed feet - were useful amid the dark lava
rock and the shady forests of its island home, where native mammal
ian predators were absent but constant threats from Red-tailed Hawk
s and Great Frigatebird
s were present. The advertising call begins with a disyllabic coo, followed by three single calls, and ends with another disyllabic coo: "Coo-oo, OO, OO, OO, Coo-oo". Each of these 5 elements takes a little less than one second.
The arid
and fairly barren Clarión Island
, some 400 km (248.5 mi) west of Socorro, has an endemic subspecies
of the Mourning Dove, Zenaida macroura clarionensis. These birds are roughly intermediate in appearance between the Socorro Dove and the mainland Mourning Doves. It is highly likely that they represent a later colonization by Mourning Doves (rather than "proto-Mourning Dove" stock), which evolved its phenotype
independently from but in parallel
with the Socorro birds. This would mean that predation by Great Frigatebirds is significant enough to select towards a cryptic
darkening of the plumage, as these are the only predators of Z. m. clarionensis. On a semidesert island such as Clarión, birds would be expected to evolve towards lighter plumage - to better withstand the heat and lack of reliable freshwater
sources - in accordance with Gloger's Rule
.
or, fatally, cats.
The last habitat
in which this dove was found is the low seasonally humid forest above 500 m ASL
. Before the introduction of cats, it seasonally descended into the lowlands where it was "common" in March 1953 for example. It may be that this coincided with the peak of the breeding season, when many birds had dependent young and dispersed widely to gather more varied food. This was the case in the Socorro Mockingbird
, the other mid-sized native landbird of Socorro, which apparently has very similar habitat preferences.
Its last refuge was dominated by endemic Guettarda insularis, Ilex socorroensis and Sideroxylon socorrense
, as well as Black Cherry (Prunus serotina), Ficus cotinifolia fig trees and Psidium socorrense guava
s, apparently all native on Socorro. At least at the time of the last record, it seemed to be dependent on intact understorey of Euphorbiaceae
(spurges and relatives)
and fern
s,
maybe because cats hunt less efficiently in these dense tangles. It is frugivorous and, as is often the case in Columbidae, might have played an important role in the reproduction of the trees which dominate its habitat. One of these (S. socorrense) is classified as Vulnerable
by the IUCN. In particular, it was found to associate with the fig trees.
Virtually nothing is known about breeding in the wild. Parallels in altitudinal migration with the equally solitary mockingbird might be taken as indication that the breeding activity peaked around March–April. In captivity, the female generally lays two white eggs in a nestbox 1-2.5 m above ground. The incubation lasts 14–17 days. The young fledge
after 14–20 days.
s, but high levels of understorey grazing by sheep may have limited the population. Human hunting might have temporarily brought down numbers, though little permanent settlement exists on Socorro. Cats were introduced apparently in the early 1970s. They do not seem to have been present in 1953.
The species reproduces no less willingly in captivity than other Zenaida doves
, provided its different ecological needs are addressed. Most of the surviving birds are in zoos and other facilities in Germany
and the USA. On October 30, 2006, the Socorro Dove was successfully bred at London Zoo
. The bird was named "Arnie", after Arnold Schwarzenegger
, with reference to his famous line "I'll be back" (on Socorro Island). However when Arnie was sexed he turned out to be a she. It is hoped that the descendants of Arnie and her relatives can someday soon be reintroduced into the wild. As of early 2006, it was being prepared to remove the sheep and to rid the island of cats. In the meantime, with the maintenance of the remaining birds, stock for reintroduction is being provided.
Dove
Pigeons and doves constitute the bird family Columbidae within the order Columbiformes, which include some 300 species of near passerines. In general terms "dove" and "pigeon" are used somewhat interchangeably...
that is extinct in the wild
Extinct in the Wild
Extinct in the Wild is a conservation status assigned to species or lower taxa, the only known living members of which are being kept in captivity or as a naturalized population outside its historic range.-Examples:...
. It was endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to Socorro Island
Socorro Island
Socorro Island is a small volcanic island in the Revillagigedo Islands, a Mexican possession lying some 600 kilometers off the country's western coast at 18°48'N, 110°59'W. The size is 16.5 by 11.5 km, with an area of 132 km².- Geology :...
in the Revillagigedo Islands
Revillagigedo Islands
The Revillagigedo Islands or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem...
off the west coast of Mexico. The last sighting in its natural habitat was in 1972
1972 in science
The year 1972 in science and technology involved some significant events, listed below.-Astronomy and space exploration:* January 5 - President of the United States Richard Nixon orders the development of a space shuttle program....
. There are not more than 200 and probably fewer than 100 purebred birds in captivity. A reintroduction programme is in the early stages of preparation.
It is a close relative of the Mourning
Mourning Dove
The Mourning Dove is a member of the dove family . The bird is also called the Turtle Dove or the American Mourning Dove or Rain Dove, and formerly was known as the Carolina Pigeon or Carolina Turtledove. It is one of the most abundant and widespread of all North American birds...
and Eared Dove
Eared Dove
The Eared Dove, Zenaida auriculata, is a New World tropical dove. It is a resident breeder throughout South America from Colombia to southern Argentina and Chile, and on the offshore islands from the Grenadines southwards. It may be a relatively recent colonist of Tobago and Trinidad...
s, particularly the former and was at one time considered its 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...
. In captivity, it hybridizes vigorously with the former and almost all privately-owned birds as well as several of the captive breeding programmes that lack a pedigree are known or strongly suspected to be such hybrids. They are excluded from the reintroduction program as there is evidence of unique adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
s in the Socorro species. The scientific name commemorates Zénaïde Laetitia Julie Bonaparte
Zénaïde Laetitia Julie Bonaparte
Zénaïde Laetitia Julie Bonaparte, Princess of Canino and Musignano was the elder daughter of Joseph Bonaparte and Julie Clary, and the wife of Charles Lucien Bonaparte, who was also her cousin...
and the American ornithologist and artist Andrew Jackson Grayson
Andrew Jackson Grayson
Andrew Jackson Grayson was an American ornithologist and artist.Grayson was the author of Birds of the Pacific Slope , which he considered to be a completion of John James Audubon's Birds of America...
.
Description
The Socorro Dove is a medium-sized, principally terrestrial dove with long legs for a Zenaida doveZenaida Dove
The Zenaida Dove is a member of the bird family Columbidae, which includes doves and pigeons. It is the national bird of Anguilla, where it is commonly referred to as a Turtle Dove. It lays two white eggs on a flimsy platform built on a tree or shrub. It also nests in rock crevices and on grassy...
. It is 26.5–34 cm long and weighs 190 g on average. In overall color pattern, it agrees with its relatives. It is considered to be a stronger-colored insular representative of the Mourning Dove
Mourning Dove
The Mourning Dove is a member of the dove family . The bird is also called the Turtle Dove or the American Mourning Dove or Rain Dove, and formerly was known as the Carolina Pigeon or Carolina Turtledove. It is one of the most abundant and widespread of all North American birds...
. The male is deep cinnamon on its head and underparts, with an ear streak like its relatives. The nape
Nape
The nape is the back of the neck. In technical anatomical/medical terminology, the nape is referred to by the word nucha, which also gives the adjective corresponding to "nape" in English, "nuchal"....
is blue-grey and the neck has an iridescent pink patch, most prominent after moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
. The upperparts are rufous brown. Female and juvenile coloration is slightly duller. The most conspicuous differences from the Mourning Dove - darker coloration and more well-developed feet - were useful amid the dark lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
rock and the shady forests of its island home, where native mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian predators were absent but constant threats from Red-tailed Hawk
Red-tailed Hawk
The Red-tailed Hawk is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West...
s and Great Frigatebird
Great Frigatebird
The Great Frigatebird is a large dispersive seabird in the frigatebird family. Major nesting populations are found in the Pacific and Indian Oceans, as well as a population in the South Atlantic....
s were present. The advertising call begins with a disyllabic coo, followed by three single calls, and ends with another disyllabic coo: "Coo-oo, OO, OO, OO, Coo-oo". Each of these 5 elements takes a little less than one second.
The arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
and fairly barren Clarión Island
Clarion Island
Isla Clarión, formerly called Santa Rosa, is the second largest, westernmost and most remote of the Revillagigedo Islands, west of Socorro Island and over from the Mexican mainland and an area ². It has three prominent peaks. The westernmost and tallest peak, Monte Gallegos, is high...
, some 400 km (248.5 mi) west of Socorro, has an endemic 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 Mourning Dove, Zenaida macroura clarionensis. These birds are roughly intermediate in appearance between the Socorro Dove and the mainland Mourning Doves. It is highly likely that they represent a later colonization by Mourning Doves (rather than "proto-Mourning Dove" stock), which evolved its phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
independently from but in parallel
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
with the Socorro birds. This would mean that predation by Great Frigatebirds is significant enough to select towards a cryptic
Cryptic
Cryptic can refer to:* Crypsis, of animals that are difficult to observe* Cryptic crossword, a crossword with cryptic clues* Cryptic era, earliest period of the Earth* Cryptic, an album by Edge of Sanity* Cryptic Writings, an album by Megadeth...
darkening of the plumage, as these are the only predators of Z. m. clarionensis. On a semidesert island such as Clarión, birds would be expected to evolve towards lighter plumage - to better withstand the heat and lack of reliable freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
sources - in accordance with Gloger's Rule
Gloger's rule
Gloger's Rule is a zoological rule which states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator. It was named after the zoologist Constantin Wilhelm Lambert Gloger, who first remarked upon this phenomenon in 1833...
.
Ecology
There is marked behavioral difference to the Mourning Dove. When Andrew Jackson Grayson discussed the species, he called it the "Solitary Dove" because he never saw more than one male and one female together. The doves, particularly the adult males, chase away their young as soon as these can fend for their own and the partners split for the time being. This too is believed to be in adaptation to the former dominance of aerial predators, lest local concentrations of birds, let alone young, unexperienced ones, would present easy targets for the hawks. Typical of many birds on mammal-less islands, Socorro Doves show little fear of humansIsland tameness
Island tameness is the tendency of many populations and species of animals living on isolated islands to lose their wariness of potential predators, particularly of large animals. The term is partly synonymous with ecological naïvete, which also has a wider meaning referring to the loss of...
or, fatally, cats.
The last habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
in which this dove was found is the low seasonally humid forest above 500 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...
. Before the introduction of cats, it seasonally descended into the lowlands where it was "common" in March 1953 for example. It may be that this coincided with the peak of the breeding season, when many birds had dependent young and dispersed widely to gather more varied food. This was the case in the Socorro Mockingbird
Socorro Mockingbird
The Socorro Mockingbird, Mimus graysoni, is an endangered mockingbird endemic to Socorro Island in Mexico's Revillagigedo Islands. The specific epithet commemorates the American ornithologist Andrew Jackson Grayson....
, the other mid-sized native landbird of Socorro, which apparently has very similar habitat preferences.
Its last refuge was dominated by endemic Guettarda insularis, Ilex socorroensis and Sideroxylon socorrense
Sideroxylon socorrense
Sideroxylon socorrense is a plant species in the family Sapotaceae. It is endemic to Mexico, occurring only on Socorro in the Revillagigedo Islands.On its island home, this small tree grows in habitat that is at least seasonally humid...
, as well as Black Cherry (Prunus serotina), Ficus cotinifolia fig trees and Psidium socorrense guava
Guava
Guavas are plants in the myrtle family genus Psidium , which contains about 100 species of tropical shrubs and small trees. They are native to Mexico, Central America, and northern South America...
s, apparently all native on Socorro. At least at the time of the last record, it seemed to be dependent on intact understorey of Euphorbiaceae
Euphorbiaceae
Euphorbiaceae, the Spurge family are a large family of flowering plants with 300 genera and around 7,500 species. Most are herbs, but some, especially in the tropics, are also shrubs or trees. Some are succulent and resemble cacti....
(spurges and relatives)
and fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s,
maybe because cats hunt less efficiently in these dense tangles. It is frugivorous and, as is often the case in Columbidae, might have played an important role in the reproduction of the trees which dominate its habitat. One of these (S. socorrense) is classified as Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
by the IUCN. In particular, it was found to associate with the fig trees.
Virtually nothing is known about breeding in the wild. Parallels in altitudinal migration with the equally solitary mockingbird might be taken as indication that the breeding activity peaked around March–April. In captivity, the female generally lays two white eggs in a nestbox 1-2.5 m above ground. The incubation lasts 14–17 days. The young fledge
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
after 14–20 days.
Extinction in the wild
The Socorro Dove is thought to have been extirpated mainly by feral catCat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, but high levels of understorey grazing by sheep may have limited the population. Human hunting might have temporarily brought down numbers, though little permanent settlement exists on Socorro. Cats were introduced apparently in the early 1970s. They do not seem to have been present in 1953.
The species reproduces no less willingly in captivity than other Zenaida doves
Zenaida Doves
The Zenaida doves make up a small genus of American doves. There are 7 species:* White-winged Dove, Zenaida asiatica* West Peruvian Dove, Zenaida meloda* Zenaida Dove, Zenaida aurita...
, provided its different ecological needs are addressed. Most of the surviving birds are in zoos and other facilities in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and the USA. On October 30, 2006, the Socorro Dove was successfully bred at London Zoo
London Zoo
London Zoo is the world's oldest scientific zoo. It was opened in London on 27 April 1828, and was originally intended to be used as a collection for scientific study. It was eventually opened to the public in 1847...
. The bird was named "Arnie", after Arnold Schwarzenegger
Arnold Schwarzenegger
Arnold Alois Schwarzenegger is an Austrian-American former professional bodybuilder, actor, businessman, investor, and politician. Schwarzenegger served as the 38th Governor of California from 2003 until 2011....
, with reference to his famous line "I'll be back" (on Socorro Island). However when Arnie was sexed he turned out to be a she. It is hoped that the descendants of Arnie and her relatives can someday soon be reintroduced into the wild. As of early 2006, it was being prepared to remove the sheep and to rid the island of cats. In the meantime, with the maintenance of the remaining birds, stock for reintroduction is being provided.