thumb|Large-billed crow in Tokyo, Japan. Note the robust beak, rounded head and iridescent black plumage.

thumb|In [[Bhigwan, Maharashtra, India.]]

The large-billed crow (Corvus macrorhynchos), formerly referred to widely as the jungle crow, is a widespread Asian species of crow. It is very adaptable and is able to survive on a wide range of food sources, making it capable of colonizing new areas, due to which it is often considered a nuisance, especially on islands. It has a large bill, which is the source of its scientific name macrorhynchos (Ancient Greek for "long-billed") and it is sometimes known by the common name thick-billed crow. It can also be mistaken for a common raven. The eastern jungle crow and Indian jungle crow were once considered conspecific and together called the jungle crow.

Taxonomy

The large-billed crow was formally described in 1837 by the German naturalist Johann Georg Wagler under the current binomial name Corvus macrorhynchos. The type locality is the island of Java. The specific epithet macrorhynchos is from Ancient Greek μακρορρυγχος/makrorrhunkhos meaning "long-billed".

The taxonomy has a long and complicated history, and is still not fully resolved.

Early in the 20th century the large-billed crow together with the Bismarck crow (Corvus insularis), Torresian crow (Corvus orru), little crow (Corvus bennetti) and Philippine jungle crow (Corvus philippinus) were all considered to be conspecific with the Australian raven (Corvus coronoides). In 1929 the German ornithologist Ernst Hartert split the expanded Corvus coronoides into several species based on the size of the throat hackles and the colour of the base of the neck feathers.

Ten subspecies are recognised. Some are distinctive vocally, morphologically and genetically, leading to treatments that raise some of them into species status.

  • C. m. japonensis Bonaparte, CLJL, 1850 – Sakhalin, Kuril Islands, and northern Japan. (includes hondoensis and borealis)
  • C. m. connectens Stresemann, EFT, 1916 – southern Ryukyu Islands (Amami Ōshima, Okinawa, and Miyako Island, southern Japan)
  • C. m. osai Ogawa, M, 1905 – Yaeyama Islands of southern Ryukyu Islands (Ishigaki, Iriomote, Kohama, Kuru, and Aragusuku, southern Japan)
  • C. m. mandshuricus Buturlin, SA, 1913 – northeastern Asia
  • C. m. colonorum Swinhoe, R, 1864 – central and southern China including Hainan, Taiwan, and northern Indochina. (includes hassi, mengtszensis and hainanus)
  • C. m. tibetosinensis Kleinschmidt, O & Weigold, MH, 1922 – eastern Himalayas to southeastern Tibet, northern Myanmar, and western China
  • C. m. intermedius Adams, AL, 1859 – far eastern Iran to northwestern India and western Himalayas
  • C. m. macrorhynchos Wagler, JG, 1827 – southern Indochina, the Malay Peninsula, Sumatra, Java, and the Lesser Sunda Islands. (includes timoriensis)
  • C. m. levaillantii Lesson, RP, 1831 – northeastern India (west to West Bengal) and eastern Nepal eastward to western Thailand, and Andaman Islands. (includes andamanensis)
  • C. m. culminatus Sykes, WH, 1832 – peninsular India and Sri Lanka. (includes anthracinus)

Two of the above subspecies have sometimes been treated as separate species: C. m. levaillantii as the eastern jungle crow and C. m. culminatus as the Indian jungle crow. The Philippine jungle crow (Corvus philippinus) was formerly also considered to be a subspecies but is now treated as a distinct species based on a phylogenetic study published in 2012 that compared mitochondrial DNA sequences.

Description

thumb|[[Subspecies|Ssp. japonensis scavenging on a dead shark]]

The large-billed crow is relatively large all-black corvid. It is in length and in weight. It has a large black bill with an arched culmen. The base of the culmen is hidden by a layer of overlapping black . The glossy black plumage has a purple sheen. The bases of the neck feathers are pale grey. The throat has elongated hackle feathers. The irises are dark brown and the legs are black. The sexes are similar in plumage but the female, on average, is smaller than the male and has a less arched culmen. The juvenile has less glossy plumage and has smoky blue rather than brown irises. The subspecies differ in overall size, the bill size and the degree of gloss on the plumage. The largest subspecies is C. m. japonensis which has a bill measuring in length. The smallest subspecies is C. m. culminatus with a bill measuring .

Hoarding behaviour has been noted in ssp. culminatus.

Breeding

thumb|right|Large-billed crow in Japan

The nest is a platform of twigs, usually high up on a tree with a preference for tall conifers like fir or pine. There are normally 3–5 eggs laid and they are incubated for 17–19 days. The young are fledged usually by about the 35th day. In India, the large-billed crow breed from March to May, but in the plains some of them start even in mid December. The nest is built in a fork of a tree, and is a shallow cup of sticks, sometimes neat and well made, sometimes sketchy and ragged; it is lined with grass roots, wool, rags, vegetable fibre, and similar materials.

thumb|upright=0.8|Eggs, [[Muséum de Toulouse]]

The normal clutch consists of four or five eggs, and rarely six or seven. The egg is a broad oval, rather pointed at the smaller end. The texture is hard and fine and there is a fair gloss. The ground colour is any shade of blue-green, and is blotched, speckled and streaked with dull reddish-brown, pale sepia, grey and neutral tint. In size the eggs average about 1.45 by 1.05 inches.

Roosting

Gregarious at roosts with many thousands at some roost sites. Large flocks may be seen at dusk arriving at major roost sites. These roosts show no apparent reduction even during the breeding season, and this is because they do not breed during their first year.

Voice

The voice is similar to the house crow to which it is closest, but deeper and usually more resonant and described as the usual loud "caa-haa-caa". However, it makes a range of calls, some which could be described as "cau cau" and others that could be mistaken for a woodpecker drumming.

Mortality factors

There are few predators of this species. Filarial parasites have been reported from this species. Pathogenic viruses such as H5N1 have been noted to cause mortality in Japan. Large scale deaths have also been noted to be caused by Clostridium infection and enteritis.

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Various views and plumages

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File:Jungle-crow-corvus-macrorhynchos.jpg|Lumpini Park, Bangkok

File:Large billed Crow (Race-intermedius) I2 IMG 3649.jpg| in Kullu District of Himachal Pradesh, India

File:Large billed Crow (Race-intermedius) I IMG 3909.jpg| in Kullu District of Himachal Pradesh, India

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References

  • Jungle crow call (two birds)
  • Long-billed crow sounds on xeno-canto.