Red-billed chough
Red-billed chough | |
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Adult of subspecies P. p. barbarus on La Palma, Canary Islands | |
Adult P. p. himalayanus in Sikkim, India | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Corvidae |
Genus: | Pyrrhocorax |
Species: | P. pyrrhocorax
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Binomial name | |
Pyrrhocorax pyrrhocorax | |
Approximate distribution shown in green | |
Synonyms | |
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The red-billed chough, Cornish chough or simply chough (
This bird has glossy black plumage, a long curved red bill, red legs, and a loud, ringing call. It has a buoyant acrobatic flight with widely spread
Although it is subject to predation and parasitism, the main threat to this species is changes in agricultural practices, which have led to population decline, some local extirpation, and range fragmentation in Europe; however, it is not threatened globally. The red-billed chough, which derived its common name from the jackdaw, was formerly associated with fire-raising, and has links with Saint Thomas Becket and Cornwall. The red-billed chough has been depicted on postage stamps of a few countries, including the Isle of Man, with four different stamps, and the Gambia, where the bird does not occur.
Taxonomy
The red-billed chough was first described by
"Chough" was originally an alternative onomatopoeic name for the jackdaw, Corvus monedula, based on its call. The similar red-billed species, formerly particularly common in Cornwall, became known initially as "Cornish chough" and then just "chough", the name transferring from one species to the other.[7] The Australian white-winged chough, Corcorax melanorhamphos, despite its similar shape and habits, is only distantly related to the true choughs, and is an example of convergent evolution.[8]
Subspecies
There are eight extant subspecies, although differences between them are slight.[9]
- P. p. pyrrhocorax, the endemic to the British Isles, where it is restricted to Ireland, the Isle of Man, and the far west of Wales and Scotland,[9] although it recolonised Cornwall in 2001 after an absence of 50 years.[10]
- P. p. erythropthalmus, described by Louis Pierre Vieillot in 1817 as Coracia erythrorhamphos,[11] occurs in the red-billed chough's continental European range, excluding Greece. It is larger and slightly greener than the nominate race.[9]
- P. p. barbarus, described by Charles Vaurie under its current name in 1954, is resident in North Africa and on La Palma in the Canary Islands. Compared to P. p. erythropthalmus, it is larger, has a longer tail and wings, and its plumage has a greener gloss. It is the longest-billed form, both absolutely and relatively.[12]
- P. p. baileyi described by Austin Loomer Rand and Charles Vaurie under its current name in 1955,[13] is a dull-plumaged subspecies endemic to Ethiopia, where it occurs in two separate areas. The two populations could possibly represent different subspecies.[9]
- P. p. docilis, described by Johann Friedrich Gmelin as Corvus docilis in 1774,[14] breeds from Greece to Afghanistan. It is larger than the African subspecies, but it has a smaller bill and its plumage is very green-tinted, with little gloss.[9]
- P. p. himalayanus, described by intergrades with P. p. docilis in the west of its range. It is the largest subspecies, long-tailed, and with blue or purple-blue glossed feathers.[9]
- P. p. centralis, described by Erwin Stresemann in 1928 under its current name,[16] breeds in Central Asia. It is smaller and less strongly blue than P. p. himalayanus,[9] but its distinctness from the next subspecies has been questioned.[12]
- P. p. brachypus, described by Robert Swinhoe in 1871 as Fregilus graculus var. brachypus,[17] breeds in central and northern China, Mongolia and southern Siberia. It is similar to P. p. centralis but with a weaker bill.[9]
There is one known prehistoric form of the red-billed chough. P. p. primigenius, a
Detailed analysis of call similarity suggests that the Asiatic and Ethiopian races diverged from the western subspecies early in evolutionary history, and that Italian red-billed choughs are more closely allied to the North African subspecies than to those of the rest of Europe.[20]
Description
The adult of the "nominate" subspecies of the red-billed chough, P. p. pyrrhocorax, is 39–40 centimetres (15–16 inches) in length, has a 73–90 centimetres (29–35 inches) wingspan,[21] and weighs an average 310 grammes (10.9 oz).[4] Its plumage is velvet-black, green-glossed on the body, and it has a long curved red bill and red legs. The sexes are similar (although adults can be sexed in the hand using a formula involving tarsus length and bill width)[22] but the juvenile has an orange bill and pink legs until its first autumn, and less glossy plumage.[9]
The red-billed chough is unlikely to be confused with any other species of bird. Although the jackdaw and Alpine chough share its range, the jackdaw is smaller and has unglossed grey plumage, and the Alpine chough has a short yellow bill. Even in flight, the two choughs can be distinguished by Alpine's less rectangular wings, and longer, less square-ended tail.[9]
The red-billed chough's loud, ringing chee-ow call is clearer and louder than the similar vocalisation of the jackdaw, and always very different from that of its yellow-billed
Distribution and habitat
The red-billed chough breeds in Ireland, western Great Britain, the Isle of Man, southern Europe and the Mediterranean basin, the Alps, and in mountainous country across Central Asia, India and China, with two separate populations in the Ethiopian Highlands. It is a non-migratory resident throughout its range.[9]
Its main habitat is high mountains; it is found between 2,000 and 2,500 metres (6,600 and 8,200 ft) in North Africa, and mainly between 2,400 and 3,000 metres (7,900 and 9,800 ft) in the Himalayas. In that mountain range it reaches 6,000 metres (20,000 feet) in the summer, and has been recorded at 7,950 metres (26,080 feet) altitude on Mount Everest.[9] In the British Isles and Brittany it also breeds on coastal sea cliffs, feeding on adjacent short grazed grassland or machair. It was formerly more widespread on coasts but has suffered from the loss of its specialised habitat.[24][25] It tends to breed at a lower elevation than the Alpine chough,[21] that species having a diet better adapted to high altitudes.[26]
Behaviour and ecology
Breeding
The red-billed chough breeds from three years of age, and normally raises only one brood a year,
The chough lays three to five eggs 3.9 by 2.8 centimetres (1.5 by 1.1 inches) in size and weighing 15.7 grammes (0.55 oz), of which 6% is shell.[4] They are spotted, not always densely, in various shades of brown and grey on a creamy or slightly tinted ground.[21]
The egg size is independent of the clutch size and the nest site, but may vary between different females.
Juveniles have a 43% chance of surviving their first year, and the annual survival rate of adults is about 80%. Choughs generally have a lifespan of about seven years,[4] although an age of 17 years has been recorded.[28] The temperature and rainfall in the months preceding breeding correlates with the number of young fledging each year and their survival rate. Chicks fledging under good conditions are more likely to survive to breeding age, and have longer breeding lives than those fledging under poor conditions.[27]
Feeding
The red-billed chough's food consists largely of insects, spiders and other invertebrates taken from the ground, with ants probably being the most significant item.[9] The Central Asian subspecies P. p. centralis will perch on the backs of wild or domesticated mammals to feed on parasites.[citation needed] Although invertebrates make up most of the chough's diet, it will eat vegetable matter including fallen grain, and in the Himalayas has been reported as damaging barley crops by breaking off the ripening heads to extract the corn.[9] In the Himalayas, they form large flocks in winter.[33]
The preferred feeding habitat is short grass produced by grazing, for example by sheep and rabbits, the numbers of which are linked to the chough's breeding success. Suitable feeding areas can also arise where plant growth is hindered by exposure to coastal salt spray or poor soils.[34][35] It will use its long curved bill to pick ants, dung beetles and emerging flies off the surface, or to dig for grubs and other invertebrates. The typical excavation depth of 2–3 cm (3⁄4–1+1⁄4 in) reflects the thin soils which it feeds on, and the depths at which many invertebrates occur, but it may dig to 10–20 cm (4–8 in) in appropriate conditions.[36][37]
Where the two chough species occur together, there is only limited competition for food. An Italian study showed that the vegetable part of the winter diet for the red-billed chough was almost exclusively
Natural threats
The red-billed chough's predators include the peregrine falcon, golden eagle and Eurasian eagle-owl, while the common raven will take nestlings.[39][40][41][42] In northern Spain, red-billed choughs preferentially nest near lesser kestrel colonies. This small insectivorous falcon is better at detecting a predator and more vigorous in defence than its corvid neighbours. The breeding success of the red-billed chough in the vicinity of the kestrels was found to be much higher than that of birds elsewhere, with a lower percentage of nest failures (16% near the falcon, 65% elsewhere).[42]
This species is occasionally
Red-billed choughs can also carry
Status
The red-billed chough has an extensive range, estimated at ten million square kilometres (four million square miles), and a large population, including an estimated 86,000 to 210,000 individuals in Europe. Over its range as a whole, the species is not believed to approach the thresholds for the global population decline criterion of the
However, the European range has declined and fragmented due to the loss of traditional pastoral farming, persecution and perhaps disturbance at breeding and nesting sites, although the numbers in France, Great Britain and Ireland may now have stabilised.[21] The European breeding population is between 12,265 and 17,370 pairs, but only in Spain is the species still widespread. Since in the rest of the continent breeding areas are fragmented and isolated, the red-billed chough has been categorised as "vulnerable" in Europe.[30]
In Spain the red-billed chough has recently expanded its range by utilising old buildings, with 1,175 breeding pairs in a 9,716-square-kilometre (3,751 sq mi) study area. These new breeding areas usually surround the original montane core areas. However, the populations with nest sites on buildings are threatened by human disturbance, persecution and the loss of old buildings.[47] Fossils of both chough species were found in the mountains of the Canary Islands. The local extinction of the Alpine chough and the reduced range of red-billed chough in the islands may have been due to climate change or human activity.[48]
A small group of wild red-billed chough arrived naturally in Cornwall in 2001, and nested in the following year. This was the first English breeding record since 1947, and a slowly expanding population has bred every subsequent year.[25]
In
In culture
Greek mythology
In
Nuisance species
Up to the eighteenth century, the red-billed chough was associated with fire-raising, and was described by William Camden as incendaria avis, "oftentime it secretly conveieth fire sticks, setting their houses afire".[7] Daniel Defoe was also familiar with this story:
It is counted little better than a kite, for it is of ravenous quality, and is very mischievous; it will steal and carry away any thing it finds about the house, that is not too heavy, tho' not fit for its food; as knives, forks, spoons and linnen cloths, or whatever it can fly away with, sometimes they say it has stolen bits of firebrands, or lighted candles, and lodged them in the stacks of corn, and the thatch of barns and houses, and set them on fire; but this I only had by oral tradition.[53]
Not all mentions of "chough" refer to this species. Because of the origins of its name, when
Cornish heraldry
The red-billed chough has a long association with Cornwall, and appears on the Cornish coat of arms.[10] According to Cornish legend King Arthur did not die after his last battle but rather his soul migrated into the body of a red-billed chough, the red colour of its bill and legs being derived from the blood of the last battle[54] and hence killing this bird was unlucky.[51] Legend also holds that after the last Cornish chough departs from Cornwall, then the return of the chough, as happened in 2001, will mark the return of King Arthur.[55]
In English heraldry the bird is always blazoned as "a Cornish chough" and is usually shown "proper", with tinctures as in nature. Since the 14th century, St Thomas Becket (d.1170), Archbishop of Canterbury, has retrospectively acquired an attributed coat of arms consisting of three Cornish choughs on a white field,[56] although as he died 30 to 45 years before the start of the age of heraldry,[57] in reality he bore no arms. These attributed arms appear in many English churches dedicated to him. The symbolism behind the association is not known for certain. According to one legend, a chough strayed into Canterbury Cathedral during Becket's murder, while another suggests that the choughs are a canting reference to Becket's name, as they were once known as "beckits".[58] However the latter theory does not stand up to scrutiny, as the use of the term "beckit" to mean a chough is not found before the 19th century.[58] Regardless of its origin, the chough is still used in heraldry as a symbol of Becket, and appears in the arms of several persons and institutions associated with him, most notably in the arms of the city of Canterbury.[59]
Other nations
This species has been depicted on the stamps of Bhutan, The Gambia, Turkmenistan and Yugoslavia.[60] It is the animal symbol of the island of La Palma.[61]
See also
References
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