Trocaz Pigeon
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The trocaz pigeon, Madeira laurel pigeon or long-toed pigeon (''Columba trocaz'') is a
pigeon Columbidae is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in some species feature fleshy ceres. ...
which is
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to the island of
Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...
,
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
. It is a mainly grey bird with a pinkish breast; its silvery neck patch and lack of white wing markings distinguish it from its close relative and probable ancestor, the common wood pigeon. Its call is a characteristic six-note cooing, weaker and lower-pitched than that of the wood pigeon. Despite its bulky, long-tailed appearance, this pigeon has a fast, direct flight. A scarce resident breeder in
laurisilva Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and el ...
forests, the trocaz pigeon lays one white egg in a flimsy twig nest. Its numbers fell sharply after human colonisation of the Madeira
archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...
, and it vanished altogether from
Porto Santo Island Porto Santo Island () is a Portuguese island and municipality northeast of Madeira Island in the North Atlantic Ocean; it is the northernmost and easternmost island of the archipelago of Madeira, located in the Atlantic Ocean west of Europe a ...
. The major cause of its population decline was
habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
from forest clearance, but hunting and nest predation by introduced rats were also contributory factors. Protection of the laurel forests and a ban on hunting have enabled numbers to increase, so that the species is no longer endangered.


Description

The trocaz pigeon is a rather plain, dark grey bird long with a wingspan. The upper back has a violet sheen, becoming green on the back of the neck, and the neck sides are patterned with silver-white. The tail is blackish with a wide, pale grey band, and the
flight feather Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the tai ...
s are mainly black. The upper breast is pinkish, the eye is yellow, the bill has a yellow tip and a reddish-purple base, and the legs are red. The sexes are similar in appearance, but the juvenile has generally browner
plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
, with limited or no development of the silvery neck patch. Its closed wings have a scaly appearance due to pale buff feather edges. The trocaz pigeon's voice is weaker and deeper than that of common wood pigeon, typically consisting of six syllables with the middle pair of notes extended and stressed: '.Mullarney (1999) p. 216. When flying, it appears heavy and large-tailed, although its flight is rapid and direct. The common wood pigeon had a poorly defined Madeiran subspecies, '' Columba palumbus maderensis''. This was paler than the trocaz pigeon and had white wing patches and a more extensive green
iridescence Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstru ...
on the
nape The nape is the back of the neck. In technical anatomical/medical terminology, the nape is also called the nucha (from the Medieval Latin rendering of the Arabic , ). The corresponding adjective is ''nuchal'', as in the term ''nuchal rigidity'' ...
, but it became extinct before 1924. Bolle's pigeon is more similar in appearance to the trocaz pigeon, although it lacks the whitish neck patch and has a more extensively pink breast. However, that species is endemic to the
Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...
, so there is no range overlap. The only other pigeon currently present on Madeira is the
feral pigeon Feral pigeons are birds derived from domesticated populations of the rock dove ''Columba livia'', descendants that have escaped and are living independently from (and often unwanted by) humans, having gone "feral". They are sometimes given the ...
; this is slimmer, has more pointed wings and a much smaller tail. It often has dark wing markings, and a lighter flight.


Taxonomy

The genus ''
Columba Columba () or Colmcille (7 December 521 – 9 June 597 AD) was an Irish abbot and missionary evangelist credited with spreading Christianity in what is today Scotland at the start of the Hiberno-Scottish mission. He founded the important abbey ...
'' is the largest within the pigeon family, and has the widest distribution. Its members are typically pale grey or brown, often with white head or neck markings or iridescent green or purple patches on the neck and breast. The neck feathers may be stiffened and aligned to form grooves. One of several subgroups within ''Columba'' consists of the widespread Eurasian common wood pigeon, Bolle's pigeon, the trocaz pigeon, and the African Afep pigeon. The two
Macaronesia Macaronesia (; ) is a collection of four volcanic archipelagos in the Atlantic Ocean#North Atlantic, North Atlantic Ocean, off the coast of North Africa and Europe. Each archipelago is made up of a number of list of islands in the Atlantic Oc ...
n endemic pigeons, Bolle's and trocaz, are thought to be derived from isolated island populations of ''C. palumbus''.Gibbs (2000) p. 175. The Atlantic archipelagos of the Canaries,
Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...
, and Madeira have a volcanic origin and they have never been part of a continent. The formation of Madeira started in the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
and the island was substantially complete by 700,000 years ago. Retrieved 20 July 2010 At various times in the past, the major islands of these archipelagos were all colonised by ancestral wood pigeons, which evolved on their respective islands in isolation from the mainland populations.
Mitochondrial A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
and
nuclear Nuclear may refer to: Physics Relating to the nucleus of the atom: *Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics * Nuclear space *Nuclear ...
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
sequences suggest that the ancestor of Bolle's pigeon may have arrived in the Canaries about 5  mya, but an older lineage that gave rise to another Canarian endemic, the laurel pigeon, ''C. junoniae'', may date from 20 mya. The most recent wood pigeon arrival on Madeira was that which gave rise to the subspecies ''C. palumbus maderensis''. The trocaz pigeon was formally described in 1829 by Karl Heineken, a German medical doctor and ornithologist who was living on Madeira at the time. He recognised it as different from the now-extinct local form of the common wood pigeon, which he called the "Palumbus", and noted that the two pigeons never interbred or habitually associated together. He suggested designating the new species by its local name, "trocaz". ''Trocaz'' is a variant of Portuguese ''torcaz'', the common wood pigeon; both words are ultimately derived from the Latin ''torquis'', a collar, and refer to the bird's coloured neck patches. This is a
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
species, although in the past Bolle's pigeon was sometimes regarded as a
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
of the trocaz pigeon.


Distribution and habitat

The trocaz pigeon is endemic to the mountainous subtropical Atlantic main island of Madeira, although it formerly also bred on the neighbouring
Porto Santo Island Porto Santo Island () is a Portuguese island and municipality northeast of Madeira Island in the North Atlantic Ocean; it is the northernmost and easternmost island of the archipelago of Madeira, located in the Atlantic Ocean west of Europe a ...
. It mainly occurs on the northern slopes of the mountains, but smaller numbers are found in the south where suitable patches of laurel forest remain. The natural habitat is tall
laurisilva Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and el ...
forest or dense tree heaths which are cloud-covered for much of the year.Snow (1998) p. 848. The forests consist mainly of laurel, '' Ocotea foetens'', Madeira mahogany, Canary laurel, faya, lily-of-the-valley-tree and '' Picconia excelsa''. The trocaz pigeon prefers primary forests, but
secondary growth In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips ...
is used for feeding, and agricultural land is also visited, especially at times of fruit shortage. Most of the pigeons are found below , and their prime environment appears to be steep ravine-indented slopes along artificial watercourses, with the occasional large dead laurel tree and much tree heath. This species is highly mobile between different areas at different times of year.


Behaviour


Breeding

Pigeons can
breed A breed is a specific group of breedable domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist seve ...
from their first year, and nesting occurs throughout the year, although mainly from February to June. The displays are similar to those of the common wood pigeon; the male climbs quickly in flight, gives a loud wing-clap, and then glides down with his wings and tail spread. The display may be repeated two or three times before the bird returns to a perch. On the ground the male performs a bowing display with his neck inflated to show off the iridescent neck patches; meanwhile, the tail is raised, fanned, then closed again. This display is usually accompanied by calling. The nest is a typical pigeon construction, a flimsy structure of twigs and grasses usually placed high in a tree in thick forest. One, rarely two, smooth white eggs are laid, although no nest with two chicks has ever been found. The eggs, in size, are incubated for 19–20 days; the young are able to fly in 28 days, and are independent within eight weeks.


Feeding

The trocaz pigeon is exclusively herbivorous. Nearly 60% of its diet is fruit, with most of the rest being leaves, and just 1% is flowers. The fruits of Til, Azores Laurel and '' Persea indica'', and the fruits and leaves of small-leaved holly are the most frequently detected food items. Most seeds pass through the digestive system intact, apart from those of Azores Laurel, which are usually damaged. Fruit is the main component of the diet when it is readily available in autumn and winter, and leaves are consumed in spring and summer when fruits are scarce. In one study, 27% of the leaves consumed came from native trees, especially Small-leaved Holly, 61% from herbs and shrubs, and nearly 10% from introduced trees, mainly apples and peaches. This pigeon will feed in agricultural areas, where cabbage is the most commonly taken crop plant. Pigeon faeces from agricultural areas contain few native plants, and samples from forests have few crop species, so some individual birds may concentrate on crops. Feeding in cultivated land is commonest in winter, when fruit is readily available, so it appears not to be a shortage of natural foods that causes them to leave the forest, but is mostly opportunistic, resulting from the birds' movements through nearby forest. However, when the fruit crop of Til and Azores Laurel is poor, large numbers of pigeons may leave the forest to feed on cabbage, flowering cherries and vine shoots.Gibbs (2000) pp. 188–189. Competition for food with rats can be significant in parts of the island.


Status

The trocaz pigeon formerly bred on both the main island of Madeira and nearby Porto Santo Island. It was very abundant when the islands were first colonised by humans, but was
extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...
on Porto Santo, and by 1986 had declined to about 2,700 birds. Hunting was banned in that year, and there are now between 7,500 and 10,000 individuals in approximately of suitable habitat. The losses on the two islands, the only inhabited ones in the archipelago, were largely the result of
deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
for
wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
and to create agricultural and grazing land. The exclusion of livestock from the native forest allows the forest to regenerate and create more suitable habitat. Some illegal hunting and poisoning continues because of the damage this pigeon can do to crops, and the government allowed a
cull Culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is removing or segregating animals from a breeding stock based on a specific trait. This is done to exagge ...
in 2004. Perhaps the main limiting factor on the rate at which the pigeon increases its numbers is
predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
by introduced
black rat The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
s on its eggs and young. The Madeira Nature Park has a management plan for the trocaz pigeon, and it is hoped that an education campaign and the promotion of bird scarers may reduce persecution. Its increasing population means that it is now classed as
Least Concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...
on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
, an improvement on its Threatened status in 1988. This species is protected under the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
Birds Directive The Birds Directive (formally known as Council Directive 2009/147/EC on the conservation of wild birds) is the oldest piece of EU legislation on the environment and one of its cornerstones which was unanimously adopted in April 1979 as the Dir ...
, and the laurel forests under the Habitats Directive.


References


Cited text

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External links

* Madeira Birds
Trocaz Pigeon
{{Taxonbar, from=Q770308 Birds described in 1829 Birds of Madeira Endemic fauna of Madeira Columba (genus) Taxa named by Karl Heineken Endemic birds of Portugal