193

Diet of Jungle Crows in an Urban Landscape
Reiko KUROSAWA1*, Ryo KONO2, Takahiko KONDO3 and Yutaka KANAI4
1

Biodiversity Lab, Institute of Low Temperature Science, Hokkaido University,
Nishi 8-chome, Kita 19-jo, Kitaku, Sapporo, Hoddaido 060‐0819, Japan
2
Ecosys 3-11-18-201, Higashi, Kunitachi, Tokyo 186-0002, Japan
3
Environmental Ecosystem Lab, Rakunogakuen University,
582-1 Midoricho, Bunkyodai, Ebetsu, Hokkaido 069-8501, Japan4
Wild Bird Society of Japan, 2-35-2, Minamidaira, Hino, Tokyo 191-0041, Japan* e-mail: rkurosawa@nifty.com

Abstract
An animal species’ diet constitutes the basic ecology of that species and is indispensable forunderstanding its population dynamics. As jungle crows have increased in the urban areas of Tokyo,
conflicts between humans and crows have increased. Since highly urbanized areas are poor in natural
food resources, it is possible that jungle crows depend heavily on human-related food in Tokyo. We
have, therefore, determined their diet and compared the results with those of other regions, taking steps
firstly, to assess the reliability of information from pellets, feces and direct observations of feeding
crows.
Jungle crows exploit a wide variety of food in response to temporal and seasonal availability inurban as well as rural areas. Their winter diet consists primarily of plant matter, suggesting that theyretain their original food habit of eating fruits and berries of trees and shrubs, even at a heavily
urbanized site. The proportion of food scraps in their diet was similar to that of animal matter in ourstudy, suggesting an unusually ample availability of anthropogenic food sources in this city. If foodscraps in Tokyo could be reduced, a great proportion of the food currently available to the crows would
be lost, driving down the carrying capacity. We suggest ecological studies be conducted before
making some action plans to solve wildlife issues.
Key words: diet, food scrap, fruit eater, jungle crow (Corvus macrorhynchos), urban landscape

1. Introduction
Jungle crows (Corvus macrorhynchos) are large
crows (body length ca. 55 cm) distributed in theforested regions of East Asia through the Far East Asia
（Madge & Burn, 1994; Iwasa et al., 2002）. They
inhabit a variety of forests, such as broad-leaved
deciduous, broad-leaved evergreen and mixed coniferous forests. Forest dwellers, as the English nameimplies, they occur in farmlands with hedges and inwooded areas of city parks as well, making them oneof the most familiar bird species to Japanese people（Higuchi, 1979; Karasawa, 2003）.
Having a close relationship with behavior as well
as morphology, feeding habits are a basic ecologicalparameter of animal species. Jungle crows are yearround residents and are reported to have a home rangeof less than 8 km in Tokyo (Morishita et al., 2003).
Therefore, the diet of this species probably reflects theecosystems of its local habitats, which implies, on theother hand, that the diet varies from region to region.

Jungle crows are known to have a wide range of foodpreferences. They feed on insects, bird eggs andchicks, while they scavenge dead animals. They eat
various fruits and seeds of trees as well, and thus theirrole as a seed disperser has been pointed out (Ueda &Fukui, 1992).
Although Jungle crows have a relationship, direct
or indirect, with a wide variety of wildlife in theirhabitats, few studies on their feeding habits have been
carried out in predominantly urban areas except for
Osaka (Ueda & Fukui, 1992).
In Tokyo, a megalopolis with 12 million people,
approximately 36,000 crows were counted in thewinter of 2001-2002 (Ueta et al., 2003). Food scraps
in this city are disposed of in transparent plastic bags
and lie outdoors until garbage trucks come to collectthem. Since the plastic bags are flimsy, they arevulnerable to scavenging by crows, cats and rats
(Kurosawa et al., 1999a). The availability of foodscraps in plastic bags on the streets is suggested to be
responsible for the marked increase in crows in Tokyo(Kawachi & Matsuda, 1999; Kurosawa et al., 2001,

194

R. KUROSAWA et al.

Ueta et al., 2003). The conflict between humans andcrows has increased as the crow population increased
in urban areas. The major complaint by the citizens
was scattering of trash on streets by scavenging crows(Ministry of the Environment, 2001; Kurosawa et al.,2003). The citizens in areas with a higher frequencyof garbage scattering had strong negative feelings
towards crows. Since highly urbanized areas arepoor in natural resources, it is possible that jungle
crows depend heavily on human-related food inTokyo.
In this paper, we have attempted to determine theecological status of this crow in a highly urbanizedarea by analyzing its diet, and comparing it with thosein other regions of Japan. In so doing, we would liketo find a new light to reflect on the state of coexistence of man and crows in Tokyo.
Jungle crows eat food, frequently tearing it into
small pieces, and they feed their young in their nests
directly from the gular pouch, making it hard to
identify the food items by video recording. They
gather at communal roosts in the evening, andregularly regurgitate indigestible portions of food aspellets (Yamagishi, 1982). Since the pellets are frequently found on the ground under the roost, they arereadily available for research workers. Food remains
in the pellets can shed some light on the feeding
environment of the crows that have discarded them.
Since the food remains in the pellets are indigestible
portions of the food the crows have taken in, however,they do not necessarily represent their food completely.
Therefore, we have compared the results of theanalyses of pellets and feces with direct observationsof feeding crows (Kurosawa, 1999), in order todetermine the reliability of pellets as an indicator of
feeding habits.

2. Methods
The study sites were communal roosts of crows inparks and a corporate institute with a large wooded
area in Tokyo; namely, Mizumoto Park, Rikugien Park,

Fig. 1 Map of study sites in Tokyo.

Tama Zoo and Hitachi Central Research Center(Fig. 1). The roosts were located in canopy-closed
parts of broad-leaved deciduous or evergreen stands
mixed with clusters of conifers (Cryptomeria, andChamaecyparis). Since almost all the crows (97%)
in Tokyo in 1999 were jungle crows (Kurosawa et al.,1999b), so we assumed that the pellets and feces
belonged to this species. Collecting pellets and feces
beneath the roosts between December 1999 andMarch 2000, we preserved them in a 75% alcohol
solution for later analysis. Cleaning by water andscreening all the specimens (44 pellets and 15 feces),
we identified them using 8-50 power microscopes.
In 1998 we observed jungle crows feeding inInokashira Park (Kurosawa, 1999).
We usedobservation data obtained during the winter months(Dec. to Mar.) for comparison.
We classified the substances identified in thepellets and feces into the following four categories:
1) Plant matter (fruits, berries, nuts, seeds, buds andother plant parts)
2) Animal matter (bones, insects, bird feathers,mammal hair, fish scales and others)3) Artificial matter (cloth, fiber, paper, plastic, metal,
glass and others)4) Unidentified substances including inorganic matter(clay, pebbles and others).
We generally identified plants and animals at a
family level, and when possible, at a species level(Asano, 1996; Yamatokeikokusha, 2000; Nakane et al.,1992). We assorted all fishes into animal matterwithout discriminating between marine and fresh
water fishes. We placed all mammal hairs in animal
matter. We excluded crow feathers from analysis as
an alien object taken in by chance.
We worked out the frequency of each category.
When a pellet contained parts of fruits, leaves, buds,
bones, insects, plastic and paper, for instance, thefrequency for plant matter was 3, animal matter 2,
artificial matter 2, and inorganic matter 0. After we
had compared the characteristics of the analyses ofpellets, feces and direct observations, we made a listshows crow roost sites.

Diet of Jungle Crows in an Urban Landscapeof food items according to the most suitable method
and compared the results with former studies inregions other than Tokyo.

3. Results
3.1 Reliabilities of pellets, feces and direct
observations as indicators of diet
The pellets of crows are reported to be shaped likebullets (Fig. 2; Yamagishi, 1982). Most of the pellets
collected at the study sites, however, came inindefinable shapes (Fig. 3), with a length up to 30 mm
and the width less than 30 mm.
Each pellet contained a variety of substances(Table 1), which suggests that a crow ingests a wide
spectrum of food in a short period of time (Kondo,
2003). Most of the pellets consisted of fragile
substances which tend to crumble easily. The largest
hard object was a 22 mm by 3 mm piece of twig andthe bulkiest object was a spherical seed with a radiusFig. 2 Bullet-shaped pellet of jungle crows reported as
typical in former studies (photo by R. Kurosawa).

Table 1

195

of 5.0 mm (family Myrsinaceae). Pieces of plastic
and mandarin orange endocarp were intact and folded(Fig. 4). Substances such as seeds, pieces of bones
and the outer chitin of insects were easy to identify.
Most of the substances contained in the feces were,
however, very small fragments of leaves, tiny seeds
less than 1 mm in diameter and other objects whichwere difficult to identify.
Plant matter was found in most of the pellets
analyzed (43/44, Table 1). Animal matter and artificial matter were contained in two thirds of the pellet
specimens (34/44). We compared the categories
based on the results of the analyses of the pellets andfeces and the result of the direct observation of
feeding crows (Fig. 5). The frequency of eachcategory statistically differed among the three sources(χ2 = 52.7057, df = 6, Ｐ < 0.001), but the differenceswere not significant between any of the pairs（Fisher’s PLSD test: F = 0, df = 2, Ｐ > 0.05; F =0.4569, df = 3, Ｐ > 0.05）.

Fig. 3 Pellet with an indefinable shape most frequently
observed in this study (photo by M. Matsuda).
Bar indicates 3 cm.

Food categories observed in the diet of jungle crows. Values show the cases with % occurrence observed in parentheses.

Food categories

Pellets

Feces

fruit

19

2

18
17
42
43 (97.7)

4
1
15
15 (100)

bones

12

1

insect parts

17

5

feathers, hairscalesTotal animal matter181
34 (77.3)

3
0
8 (53.3)

cloth, paper
plastic, metal etc.
Artificial objects

18
23
34 (77.3)

3
3
6 (40.0)

plastic, styrofoam, aluminum foil, paper
glass, fiber (mainly cotton)

pebble, clay, unknown
Inorganic and/or unidentified matters
Total

25
25 (56.8)44

88 (40.0)
15

stones, clay, shells

seeds
buds
leaves, stalks, roots etc.
Total plant matter

Major items (Genus/species & family)
Citrus (Rutaceae), Rubus (Rosaceae), Rhus (Anacardiaceae),
Diospyros kaki (Ebenaceae), Ardisia (Myrsinaceae), Quercus
myrsinaefolia (Fagaceae), Castanea crenata (Fagaceae)
Poaceae

Hierodula patellifera (egg case), Rhomborrhina japonica & other
Scarabaeidae
birds, mammals
fish, reptiles

196

R. KUROSAWA et al.

Fig. 4

Orange endocarp and egg case of mantis observed in asingle pellet (photo by R. Kono).

Fig. 5

Proportion of food categories of jungle crows in eachsample source.

A balanced proportion of all categories was
represented in pellets, whereas a large proportion ofunidentified matter was seen in direct observations.
On the other hand, artificial matter tended to be
identified best in the direct observations, which
frequently revealed the origin of the food items.
Parts of insects, fruits and seeds were best
represented in pellet analysis, because the pellets
contained larger pieces of indigestible substances than
did feces. Direct observation had the advantage ofidentifying large food items as crows handled them.
The analysis of pellets was, on the other hand,
effective at identifying small food items containing
indigestible substances that defied direct observation.
In addition, pellets were easy to collect. In contrast,
feces had the lowest rate of identification, indicatingthat they are not suitable materials for determining
crows’ diets.
Therefore, we used pellet analysis to determine thecrows’ diets, complementing its short-comings withthe direct observation of feeding crows. The analysis
of pellets could allow for comparison between
different regions, if conducted under a standardized
method and categorization.

3.2 Details of jungle crow diets in Tokyo
Plant matter was found in almost all of the pellets
analyzed (97.7%; Table 2). Most nutritional among
this were fruits and berries of trees and shrubs. The
plant species found in the crows’ diets seemed toreflect the regional flora, because they were common
in the Tokyo region both in natural and cultivatedlandscapes. Mandarin oranges (Citrus deliciosa,
Rutaceae), chestnuts (Castanea crenata, Fagaceae)
and persimmons (Diospyros kaki, Ebenaceae) areprobably common food sources for crows. Seeds ofPoaceae were also contained in the pellets, indicatingthat jungle crows fed on grass seeds in winter inTokyo as they do in more agricultural regions also
(Suzuki, 2002).
Second in frequency to plant matter in the pellets
were artificial and animal matters (77.3%). The
most common substances (17/44 cases) among theartificial matter were small pieces of white ortransparent plastic bags usually used as garbage bagsin Tokyo. The pellets also contained aluminum foil,
Styrofoam and paper, all of which are used for foodwrappings, suggesting their association with foodscraps. Other inorganic matter, such as pebbles andclay were also found in the pellets.
The most frequent animal matter was insects, suchas the ootheca (egg cases) of mantises (Hierodula
patellifera, Mantidae), and beetles (Sacarabedae).
The same groups of insects were reported in previous
studies in rural regions (Ikeda, 1957; Suzuki, 2002).
Most of the mammal hairs were human hair, which
has a probability of being taken in by chance as thecrows scavenged food scraps at garbage collection
sites.
Table 2 shows the results of direct observation of
feeding jungle crows (Kurosawa, 1999). Jungle
crows were observed eating a variety of fruits andberries of trees, supporting the result of the pellet
analysis. They were also observed to carry fruits ofRhus succedanea (Anacardiaceae) ， Zanthoxylum
ailanthoides (Rutaceae)，Diospyros kaki，and genus
Citrus species to their roosts (Reiko Kurosawa pers.
observ.). We found saplings of Rhus succedanea,
Zanthoxylum ailanthoides and Ardisia japonica(Myrsinaceae) under the roost sites.
Jungle crows were often observed scavenging foodscraps in dustbins, in picnic areas, and at sites where
people feed birds and fish. On a few occasions, they
were observed snatching bags of snack food directly
away from stalls in a park (Kurosawa, 1999). Thus,
they readily use human food resources in Tokyo.
Animal matter identified in direct observations
included rats, cats, feral rock doves, frogs, snails andearthworms. In addition, songbirds, such as fledgling Gray Starlings and Tree Sparrows were taken in
May and June (Table 2).

Diet of Jungle Crows in an Urban Landscape197

Table 2 List of food items of jungle crows found by direct observation (Kurosawa, 1999; with permission
from WBSJ).
Plant matter
Fruits(including berries, nuts and beans)

Animal matter
Mammal
Bird

OthersEriobotrya japonica (Rosaceae)
Diospyros kaki (Ebenaceae)
Viburnum odoratissimum (Caprifoliaceae)
Rhus succedanea (Anacardiaceae)
Aphananthe aspera (Ulmaceae)
Sweda controversa (Cornaceae)
Magnolia praecocissima (Magnoliaceae)
Gleditsia japonica (Leguminosae)
Rats & mice (Muridae)
Cats (Felis catus) (young)Rock Doves (Columba livia)
Grey Starlings (Sturnus cineraceus) (young & eggs)
Tree Sparrows (Passer montanus) (young & eggs)
Land snails (Gastropoda)
Earthworms (Oligocchaeta)

4. Discussion
The habit of procuring a wide variety of food in
response to temporal and seasonal availability was acommon feature among jungle crows in urbanized aswell as rural areas (Ikeda, 1957; Liu et al., 1986).
Among these, the major food substance was plantmatter such as fruits and berries of trees and shrubs.
The fruits of genus Rhus in particular were reported asa food item of jungle crows in previous studies (Ikeda,
1957; Yamagishi, 1982; Ueda & Fukui, 1992; Suzuki
2002), suggesting that these fruits are a common andimportant food resource for this species. Therefore,
jungle crows also retained their original food habit ofeating fruits and berries of trees in a heavily urbanizedsite as Tokyo.
The second most important food substances for thejungle crows in Tokyo were both artificial and animal
matters. The latter represents a natural food sourcecommonly observed in the previous studies throughout this crows’ range (Ikeda, 1957; Yamagishi, 1982;
Liu et al., 1986; Suzuki, 2002; Kondo, 2003).
However, the high frequency of artificial substances
would be a characteristic of crows’ diets in Tokyo.
There was a significant difference in the proportionof artificial substances found in jungle crows’ dietamong regions: 77% in Tokyo, and 7.7% and 7.9% in
the agricultural areas of Tsuruoka City, Yamagata
Prefecture (Suzuki, 2002), and Ebetsu City, Hokkaido(Kondo, 2003) respectively (χ2 = 103.42, df = 2, P <0.001; Fig. 6). If we consider marine fish, mandarinoranges and human hair as taken from food scraps, theproportion of crows’ dependence on human-related
food source is even greater. The high frequency ofartificial substances in jungle crows’ diets suggests a
greater availability of anthropogenic food sources inTokyo. Therefore, it is highly probable that thecarrying capacity of jungle crows was unnaturally
raised, contributing to an increase of this species inurban landscapes. If food scraps in Tokyo could be
reduced, a significant proportion of food currently

available to the crows would be lost. Since no life
can sustain itself far above the carrying capacity, thepopulation of crows would follow suit.
Jungle crows feed on insects such as Scarabedae
beetles and mantis in winter when insects are notactive. These insects are common in a wide range of
habitats and are probably food sources for jungle
crows in a natural state. The beetles are primaryconsumers of plants, and mantis is a predator in thefood web. The predation of these insects has aprobability of increasing biodiversity at the levels of
producers and primary consumers of forest ecosystems （Kullberg & Ekman, 2000）. Control of one
organism will inevitably affect the other organisms in
the food web, and history warns us against excessive
hunting/controlling of crows because their removal
has resulted in a population explosion among insects,
such as beetles and grasshoppers, greatly damaging
the regional economies (Forbush, 1927; Inugai &Haga, 1953).
During the breeding season, jungle crows are
known to prey on the nests and young of other bird
species, including larger birds of prey in Tokyo (Ueta,

Fig. 6

Different frequencies of artificial substances found inpellets of jungle crows in urban (Tokyo) and rural(Tsuruoka and Ebetsu; Suzuki, 2002; Kondo, 2003)
areas.

198

R. KUROSAWA et al.

1998). In winter, however, bird remains were notfound in the pellets in our study, suggesting that thecrows capture eggs and chicks of other birds primarily
during the breeding season, probably to meet thedemand of growing young. Thus, jungle crows were
not a major predator on small bird species in winter inour study sites.
The natural inorganic matter such as pebbles andclay found in crows’ pellets in our study supports
previous reports of their frequency in the pellets ofcrows (Liu et al., 1986; Suzuki, 2002; Kondo, 2003).
Among the hypotheses is that crows deliberately takein ashes for nutrition (Takenaka, 2003). An analysisof the nutrient values and experiments on theimportance of inorganic matter will be required todetermine this issue.

Acknowledgements
Shigeharu Koshikawa helped us identify plantseeds. Nanae Kato lent us a microscope. Michio
Matsuda as well as the assistant researchers of theWild Bird Society of Japan cooperated in collectingpellet and fecal samples at crow roosts. Kazuji
Fukui translated an article into Japanese.
The
Hitachi Central Research Center, park offices of
Rikugien, Mizumoto and Tama Zoological parks gave
us permission to conduct research at these sites.
Takashi Kurosawa read and gave advice on the earlymanuscript. We would like to express our sincere
gratitude to all these people.
References
Asano, S. (1996) Genshoku Zukan; Mebae to Tane (Coloredguide to the seeds and seedlings. Zenkoku Noson Kyoiku
Kyokai, Tokyo. (in Japanese)
Forbush, E.H. (1927) Birds of Mass. and other New EnglandStates, Vol. 2.
Higuchi, H. (1979) Habitat segregation between the Jungle
Crow and the Carrion Crow (Corvus macrorhynchos, C.
corone), in Japan. Japanese Journal of Ecology, 29:353-358.
Ikeda, S. (1957) Karasuka ni zokusuru chourui no shokusei ni
tsuite (On the food of Corvus species). Forestry Agency
Report on Wildlife, Tokyo. (in Japanese)
Inugai, T. and R. Haga (1953) Hokkaido niokeru karasu no
higai to bojono kenkyu (III) Tokuni karasu no shokusei tonogyo tono kankei (A study on crows concerning agricultural
impact and guarding of the crop (III) -Relation between
crows diet and agriculture). Report of Hokkaido University
Agriculture Department, 1(4):459-484. (in Japanese)
Iwasa, M.A., A.P. Kryukov, R. Kakizawa and H. Suzuki (2002)
Differentiation of Mitochondrial Gene of Jungle Crow
Corvus macrorhynchos (Corvidae) in East and South Asia.
Journal of Yamashina Institute for Ornithology, 34:66-72.
Karasawa, K. (2003) Karasu wa dorehodo kashikoika (Howwise are crows?). Chukobunko, Tokyo. (in Japanese)
Kawachi, H. and M. Matsuda, eds. (1999) A report on the
symposium “How should we deal with the crow problems inTokyo? (I).” Tokyo Chapter, Wild Bird Society of Japan,
Tokyo. (in Japanese with English summary)

Kondo, T. (2003) The diet of Carrion and Jungle Crows Corvus
corone and C. macrorhynchos living in Nopporo Forest Parkand its surroundings during the breeding season. Bachelor’s
thesis, Rakuno Gakuen University, Ebetsu, Hokkaido.
Kullberg, C. and J. Ekman. (2000) Does predation maintain tit
community diversity? OIKOS, 89:41-45.
Kurosawa, R. (1999) The life of Jungle Crows (Corvus
macrorhynchos) in Inokashira Park. In: H. Kawachi and M.
Matsuda, eds., How should we deal with the crow problemsin Tokyo? (1), Tokyo Chapter, Wild Bird Society of Japan,
Tokyo, pp.16-31. (in Japanese with English summary)
Kurosawa, R., M. Narusue, H. Kawachi and K. Suzuki (1999a)
The relationship between Jungle Crows Corvus macrorhynchos and garbage in Tokyo. Strix, 18:71-78. (inJapanese with English summary)
Kurosawa, R., M. Narusue, H. Kawachi and K. Suzuki (1999b)
Crows and garbage in Tokyo (a preliminary report, June
1999. In: Kawachi, H. and M. Matsuda, eds., How should wedeal with the crow problems in Tokyo? (1), Tokyo Chapter,
Wild Bird Society of Japan, Tokyo, pp.13-22. (in Japanesewith English summary)
Kurosawa, R., M. Narusue, H. Kawachi and K. Suzuki (2001)
Relation of Jungle Crows and garbage in Tokyo II –Comparison between summer and winter seasons. Strix,
19:71-79. (in Japanese with English summary)
Kurosawa, R., Y. Kanai, M. Matsuda and M. Okuyama (2003)
Conflict between Humans and Crows in Greater Tokyo:– Garbage Management as a Possible Solution –. Global
Environmental Research, 7(2): 139-147.
Liu, H.J., J.Q. Ren and Y.E. He. (1986) A basic research on thediet of Jungle Crows. Journal of Zoology, (2):7-10. (inChinese)Madge, S. and H. Burn (1994) Crows and Jays. Helm A & C
Black, London.
Ministry of the Environment. (2001) Jichitai tantosha
notameno karasu taisaku manual (Crow management
manual for the administrators). Ministry of the Environment,
Tokyo. (in Japanese)
Morishita, E., Kiyoshi Itao and H. Higuchi. (2003) Movements
and habitat use of crows in urban areas, based on PHS
tracking. Global Environmental Research, 7(2): 181-191.
Nakane, T., J. Aoki and R. Ishikawa. (1992) Common Insects ofJapan in Color. Hoikusha Publishing Co. Ltd, Osaka. (inJapanese)
Suzuki, Y. (2002) Hashibosogarasu Corvus corone andHashibutogarasu C. macrorhynchos no shokusei oyobi shoka
koso (Diets and digestional enzymes of Corvus corone and C.
macrorhynchos). Master’s thesis, Yamagata University,
Tsuruoka City, Yamagata. (in Japanese)
Takenaka, M. (2003) Crows Problems in Sapporo Area. Global
Environmental Research, 7(2): 149-160.
Ueda, K. and N. Fukui. (1992) Fruit food of crows Corvus
corone and C. macrorhynchos: Analysis of seeds collected at
the pre-roosting sites. Japanese Journal of Ornithology,
40(2):67-74. (in Japanese with English summary)Ueta, M. (1998) Crow-related low nesting-success of small
open-nesting birds in Tokyo area. Strix, 16:67-72. (inJapanese with English summary)Ueta, M., R. Kurosawa, S. Hamao, H. Kawachi and H. Higuchi.
(2003) Population Change of Jungle Crows in Tokyo. Global
Environmental Research, 7(2): 131-137.
Yamagishi, S. (1982) Pellet no shirabe kata (How to studypellets). In: Haneda, K., ed., Yacho no seikatsu (The life ofbirds), Tsukijishokan, Tokyo, pp.169-172. (in Japanese)
Yamatokeikokusha. (2000) Yamakei handy zukan, series 3-5(Yamakei handy guide to tree flowers). Genshokuzukan.
Yamatokeikokusha, Tokyo. (in Japanese)(Received 31 October 2003, Accepted 2 December 2003)