Bird Research News

Vol.4 No.7

2007.7.17.

Large-billed Crow

Hashibuto-garasu (Jpn) Corvus macrorhynchos

Morphology and classification
Classification: Passeriformes Corvidae
Total length: 540-600mm
Tail length: 205-255mm
Tarsus length: 52-69mm

Wing length:316-400mm
Culmen length: 62.0-76.5mm
Weight:570-895g

The measurements of adult birds after Kuroda (1970) and Tamada (2004).

Appearance:
Large-billed Crows are black all over.
Adult birds have blue to purple metallic
sheen especially in the flight feathers,
but juveniles have dull brownish flightfeathers. The inside of a mouth is blackin adults and red in juveniles. The irisis almost black in adults, but bluishgray in fledglings.

Vocalization:

Egg:

The most common call is "Kaa", butthey have a wide variety of calls. For
instance,they call "Ah-", "Core" and"Awa" in a clear voice, while they utter"Gurr" and "Gore" thickly when threatening.

Photo 1. Large-billed Crow

Distribution and Habitat
Outside of Japan Large-billed Crows are distributed in the Russian
Far East (Kamchatka, Sakhalin and Primoriskii), eastern China, theKorean Peninsula, Mongolia, the Tibetan Plateau and from Afghanistan to Southeast Asia including a part of the IndonesianIslands and the Philippines (Goodwin 1986). In Japan they range
from Hokkaido to Okinawa Island, but Large-billed Crows distributed from Amami-oshima Island to Miyakojima Island and thoseoccurring in Iriomote and Ishigaki Islands are classified into Corvus macrorhynchos connectens and C. m. osai, respectively.

Habitat:
Large-billed Crows occur in forests, coasts and urban areas, butthey are not abundant in farmland. Although there are studies on
the ecology of Large-billed Crows living in urban areas, the detailsof the life in the forest that is assumed to be their original habitat isstill unknown.

Life history
23456breeding period7891011 12juvenile
independence wintering period

Breeding system:
They are monogamous and maintain their pair-bond over several
years. Both males and females defend their territory. The territory
size varies from 2 to 49 ha (Kuroda 1981, Matsubara 2003), but it
is mostly 5-6 ha in urban areas.
It is unknown when and how pairs are formed. There is an observation record of the pair which was assumed to start breeding at
the age less than two (Kurosawa 2000), but another report suggested that it took three years to start breeding (Kuroda 1981). There
are flocks of non-breeders throughout the year, and they are assumed to consist primarily of young birds before breeding.

Nest:

42

Large-billed Crows generally build a nest in an ever-♪ http://www.bird-research.jp/1_shiryo/koe/hashibuto_060429_kokubunji_mju.mp3
Mutsuyuki Ueta

The clutch size is 4-6 eggs.
The egg size is about
45mm in the major axis.
The color is pale greenish
brown to pale greenish
blue with dark brown
flecks.

Photo 3. Eggs of Large-billed Crows.
[Yoshihide Shibata]

Incubation and nestling periods and fledging rate:

Distribution:

1

green tree at a height of 10-20m. Some of them nest in roadsidetrees and on utility poles. The nest is plate-shaped and 50-60cm inthe outer diameter. They use twigs for the exterior, but often wire
clothes hangers in urban areas as well. They line the inner cup
with fur, dead grass andthe fibers of untwined
ropes. Two or more nests
are often found in a territory because there remain anunfinished nest, an abandoned nest after breeding
failure and the remains ofan old nest. Althoughsome view that the crows
make extra nests to prevent the detection of a true Photo 2. Three nests in a row [EmikoMorishita]
nest ("camouflage nest
hypothesis"), there is yet
no evidence to support it.

Large-billed Crows lay eggs from late March to April. The incubation period is about 20 days and nestlings are brooded for about
two weeks after hatching. Females mostly incubate eggs and nestlings. Males feed their incubating mate, but they rarely deliver
food to the nest. They usually pass it to their mate near the nest or
place it on a branch.
Both males and females feed nestlings, when they carry food directly to the nest. The nestling period is about 30-35 days andnestlings begin to fledge in late May. Young spend two or threemonths with the parents after fledging. The study conducted inKyoto showed that the mean number of fledglings was about twobirds with a range of 0-4 birds. In Tokyo, on the other hand, thefledging rate is 49.7% and the mean number of fledlings is 1.1
birds (Kurosawa & Matsuda 2003).

Diet and roost
Large-billed Crows are omnivorous (Ikeda 1957). The diet consists
principally of fruits, such as cherries, hackberries, camphor berries, Rhus verniciflua, R. javanica and ivy (Ueda & Fukui 1992),
insects, birds (including eggs, nestlings and fledglings) and animal
carcasses. They may occasionally capture rock pigeons. In urban
areas they tear plastic garbage bags apart at a garbage station andscavenge for food scraps (Kurosawa 2003). They frequently cache
food as well.
Large-billed Crows are also famous for forming a communal roost,which is often shared with Carrion Crows (C. corone).

Topics of ecology, behavior and conservation● Long-distance commute to the feeding site
The pair of Large-billed Crows that the author studied in Kyoto
City nested in a Shinto shrine on the right side of the Takano River. The pair primarily used as a feeding site the garbage station in alarge housing complex on the left side of the river. But a pair ofBird Research News

Vol.4 No.7

2007.7.17.

© Japan Bird Research Association
Sumiyoshi 1-29-9, Fuchu, Tokyo, Japan
Carrion Crows defended as their territory the riverbed of the Takano River between the nest and the garbage station. When heading
for the garbage station on the other side, the Large-billed Crowpair took a shortcut across the riverbed without striking back at theterritory owners if they tried to chase the pair off. Once the pair
had crossed the river, however, it perched on a utility pole andbegan to call threateningly toward the territorial Carrion Crows.
Large-billed Crows may rarely use a feeding site detached fromtheir breeding territory like this pair.
Then, do Large-billed Crows not forage for food in a riverbed?
The study conducted in Kyoto City showed that they mostly stayedin high places such as trees and the time spent on the ground represented less than 10% (Fig. 1.) They did not scavenge for garbage
on the ground for a longtime, but flew away 1 0 0
quickly with a food80
scrap. They hardly evertree
turned stones over or60
shoved fallen leaves
aside, looking for food as40
Carrion Crows often do,
20
which suggests that thegroundriverbed was not worth0
the trouble of expelling
Large-billed Crow Carrion Crow
the Carrion Crow pairand possessing as a feed- Fig. 1. Proportion of the time (%) crows
spent during the observation.
ing site.

● Effects of the change of food supply on home range andbreeding performance

Number of fledglings

City-dwelling Large-billed Crows usually depend heavily on
kitchen garbage. How does the change of garbage availability
affect them? A pair of Large-billed Crows happened to nest near
the author's house and often scavenged for food scraps at a garbage station in the neighborhood. One day the garbage station wascovered with a protective net against crows. Then the pair moved
to another garbage station to forage for food. But this station wasalso covered with a net. The pair moved to another station again.
The pair changed its home range every time a garbage station wascovered with acrow net. In addi3tion, the number offledglings of the2pair tended to decline as the numberof available gar1
bage stations decreased (Fig. 2).
00
1234
The decrease offood supply due toNumber of garbage stations
netting may have Fig. 2. Number of garbage stations available toaffected the breedLarge-billed Crows and number of fledglings
ing performance ofof the year. The mean number is shown when
the pair (Matsubara
they nested twice. (From Matsubara 2003).
2003).

● What is known and what is still unknown
Researches show that the non-breeding Large-billed Crows ofTokyo leave their roosts around dawn for urban areas to scavenge
for food scraps. They spend the rest of the day in parks and green
spaces until returning to their roosts in the late afternoon. It isassumed that they frequently change their roosts and feeding sites(Morishita et al. 2003).
A study also indicates that Large-billed Crows have a gathering

バードリサーチ生態図鑑
call as Ravens (Corvus corax) (Soma & Hasegawa 2004), whichsuggests that they sometimes summon their companions.
In addition, the brain and cognitive studies of Large-billed Crows
show that they are a quick learner with a long memory, which isprobably related to food caching behavior and the complex relationship between individuals in their society.
The process of pair formation or the social structure, on the otherhand, is still unknown in Large-billed Crows. There is also limited
information on their breeding density and reproductive success.
Large-billed Crows are not easy to observe in their range except
for Japan because they generally occur in mountains and forests. I
think, therefore, that they should be better studied in Japan where
they are commonly found in the vicinity of humans.

Literature
Goodwin D. 1986. Crows of the World. 2nd Edition. British Museum(Natural History), London.
Ikeda S. 1959. On the diet of Corvidae. Bulletin of Wildlife Study Vol. 16.
The agriculture and forestry ministry Forestry Agency, Tokyo. [J]Kuroda N. 1970. Various measurements and stomach contents of Jungle
Crows in Tokyo. J. Yamashina Inst. Ornithol. 6:73-81. [J+E]
Kuroda N. 1981. Observation of a buff-colored Jungle Crow and the territory life. J. Yamashina Inst. Ornithol. 13:69-81. [J+E]
Kurosawa R. 2000. A process of territory establishment by a pair of Jungle
Crows Corvus macrorhynchos. Strix 18:131-135. [J+E]
Kurosawa R., Kono R., Kondo T. & Kanai Y. 2003. Diet of Jungle Crowsin an Urban Landscape. Global Environmental Research 7:193-198.
Kurosawa R. & Matsuda M. 2003. Breeding performance of crows inTokyo. Strix 21:167-176. [J+E]
Matsubara H. 2003. Comparative study of territory structure and habitat
use in syntopic corvids, the Jungle Crow (Corvus macrorhynchos) andthe Carrion Crow (C. corone). Ornithological Science 2:103-112.
Matsubara H. 2003. Some effects of the net covering of garbage stations on
the home range and reproductive success of a pair of Jungle Crows.
Strix 21:207-213. [J+E]
Morishita E., Itao K., Sasaki K. & Higuchi H. 2003. Movements of Jungle
Crows in Urban Areas, Based on PHS Tracking. Global Environmental
Research 7:181-191.
Soma M. & Hasegawa T. 2003. Formation of foraging flocks with recruitment calls in Jungle crows, Corvus macrorhynchos. Japn. J. Ornithol.
52:97-106. [J+E]
Tamada K. 2004. Sexual differences in the external measurements of Carrion and Jungle Crows in Hokkaido. Japn. J. Ornithol. 53:93-97. [J+E]
Ueda K. & Fukui N. 1992. Fruit food of crows Corvus corone and C.
macrorhynchos: analysis of seeds collected at the pre-roosting sites.
Japn. J. Ornithol. 40: 67-74. [J+E]
Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

AuthorHajime MATSUBARA

Graduate School of Science Ethology
Laboratory, Kyoto University

I once called "Kaa", looking up at crows when they returned to theroost over my house. To my surprise, some of the crows responded tomy call. When I think of it now, they may have called at that time bysheer chance. But I have started to lookat crows since then. It has been morethan ten years since I began to study
the behavior of crows in a graduate
school. Since there are many unknowns in crows (especially Largebilled Crows) and I have various
themes to pursue, they are likely to be
my long time partners.
hajime@um.u-tokyo.ac.jp

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