Bird Research News

Vol.4 No.5

Grey-faced Buzzard

2007.5.15.

Sashiba (Jpn) Butastur indicus

Morphology and classification
Classification: Galliformes Phasianidae
Total length:
Wing length:
Tail length:
Culmen length:
Tarsus length:
Weight:♂ 381-431mm (n=20)♂ 290-330mm (20)♂ 181-216mm (20)♂ 19-29mm (20)♂ 56-66mm (19)♂ 390-500g (20)♀ 400-415mm (6)♀ 313-355mm (6)♀ 195-201mm (6)♀ 21-28mm (6)♀ 51-68mm (6)♀ 430-575g (5)Measurements are of adult birds in Chiba and Okinawa Prefectures by Azuma. The
weight is of the breeders in Chiba Pref.. The English name is after Del Hoyo et al(1994).

Appearance:
Males and females are similar inplumage coloration. Adult birds
are reddish brown on the upperpart. The face is gray and abold streak runs vertically in the
middle of the throat. The chest isbrown or dark brown with brownor dark brown lateral bars on theabdomen. The tail is ashy brown
Photo 1. Grey-faced Buzzard
with four dark brown horizontal
parent with its nestlings
bars. The iris is bright yellow.
[Hiroshi Uchida]
Juveniles are less reddish on theupperpart with dark brown vertical stripes from the throat to theabdomen. The face and eye is brown with a buff-colored distinct
superciliary. Dark-morph birds which are dark brown all over are
infrequent. The wings look narrow and pointed in flight. The flightfeathers are thin and look transparent against a bright sky. Greyfaced Buzzards are thinner than similar looking Northern Goshawks (Accipiter gentilis) and Common Buzzards (Buteo buteo).
They fly linearly, flapping the wings intermittently.

Vocalization:
Males and females frequently call "Pic-qeee" or "Kim-mee" withthe accent on the first syllable in the breeding grounds, but theyoccasionally call like this in the wintering grounds and stopoversites as well . The alarm call is the same.

Distribution and Habitat
Distribution:
Gray-faced Buzzards breed in Japan as well as the Russian Far
East (the southern part of the Amur region and the Ussuri region)
and China (from the Northeast region to Hebei Province). In Japan, however, they are not confirmed to breed in Hokkaido(northernmost main island) and Okinawa Prefecture (southernmostprefecture), with only sporadic breeding reported from Aomori
Pref. (northernmost prefecture of Honshu). They winter in theNansei Islands of Japan, Taiwan, southern China, Myanmar(Burma), Indo-China, the Malay Peninsula, the Philippines, Borneo, Sulawesi (Celebes), the Moluccas Islands and New Guinea.

Habitat:More than 90% of the breeding grounds in Japan were located infoothills and plateaux with woods and rice fields at an elevation ofless than 500m (asl). Of the rice fields 90% was what is called"Yatsuda (a rice field at the bottom of a hill)" (Azuma 2004). Inshort, their typical breeding habitat is a "Satoyama (hilly countryside)" with Yatsuda. They breed in a riparian wood and woodland
adjacent to a marsh or occasionally in the mountains. Gray-faced
Buzzards wintering in Japan use a Satoyama with Yatsuda in Iriomote Island and farmland with meadows, cane fields and shelterbelts in Ishigaki and Miyako Islands (southernmost island groups).

4♪ http://www.bird-research.jp/1_shiryo/koe/sashiba060722_ichikai_mju.mp3
Mutsuyuki Ueta

Life history
123

4

5

6

wintering migration breeding
period7891011 12

independenceof juvenile

Breeding system:
Most Gray-faced Buzzards are a monogamous breeder (Kojima1987), but there is a rare report of polyandrous breeding that afemale bred with two males (Maezawa 1990).

Nest:
Gray-faced Buzzards use as a nest tree conifers, such as Japanese
red pines (Pinus densiflora) and Cryptomeria and broad leavedtrees, such as Quercus acutissima, q. serrata and Castanopsis
sieboldii, but Japanese red pines by far predominate among thenest trees. They build a nest with twigs at the base of a lateralbranch and a fork in a tree. The nest is usually one size larger thanthat of Large-billed Crows (Corvus machrorhynchos). The samenest is sometimes used every year. Though Gray-faced Buzzards
generally build a nest in the woods on a slope facing an open habitat such as rice fields, they occasionally build it in a riparian forest
and the woods of flatland as well.

Egg:
They lay eggs from late April to early May. The most common
clutch size is three eggs, with a range of 2-4 eggs (Kojima 1987).

Incubation and nestling periods:
Females mostly incubate eggs and nestlings. Males relieve females
briefly a few times a day. Eggs hatch from late May to early June
about a month after they were laid. Nestlings fledge from late Juneto early July about 35 days after hatching. Fledglings are fed by
the parent birds around the nest for about two weeks, and thenbecome independent, starting to move a long distance (Nonaka &Nagano 2006).

Migration:
Grey-faced Buzzards arrive in the breeding grounds of Japan fromlate March to early April. It is assumed that males arrive in thebreeding grounds a little ahead of females and wait for them, defending the territory. After females arrive, courtship feeding, copulation and nest building are carried out. Gray-faced Buzzards set
out on their autumn migration and head south in flocks from late
September to mid-October. A kettle of several dozen to several
hundred birds is observed at stopover sites.

Diet and foraging behavior
They perch on a tree or a utility pole adjacent to an open habitat,such as rice fields, cropland and clearings, and swoop down tocapture by feet small animals occurring in a Satoyama, such asmammals (Microtus montebelli and Urotrichus talpoides), birds(Passer montanus and Emberiza cioides), reptiles (Elaphe quadrivirgata and Takydromus tachydromoides), amphibians (Ranaescullenta and R. japonica), crustacians (Procambarus clarkii andGeothelphusa dehaani) and young of insects (Locusta migratoria,Graptopsaltria nigrofuscata and Antheraea yamamai).
Breeding males of Grey-faced Buzzards spent about 90% of thedaytime perching on a tree or a utility pole to hunt prey. They wereperched at one place for about ten minutes on average and changed
the perching spots about 60 times a day. The distance between
perching spots was several to several dozen meters and more than
90% of the perching spots were located within 500m from the nest
(Azuma 2004). In short, they adopted a search-and-ambush hunting method to reduce the flight cost for hunting and food transfer.
In a "Satoyama" with "Yatsuda", Gray-faced Buzzards prey primarily on frogs around rice fields from their arrival at the breedingBird Research News

Vol.4 No.5

2007.5.15.

© Japan Bird Research Association
Sumiyoshi 1-29-9, Fuchu, Tokyo, Japan

habitat ratio %grounds to the 100 n=14 n=16 n=15 n=21 n=27 n=8
midairearly nestling pericoppice80
od. From the midfield & meadow
farm roaddle to late nestling60
fallow &period, however,abandoned rice fields
40
levee & banktheygradually
20
rice fieldmove their foraging sites to coppic0
Early-mid Late Early Mid Late Early-mid
es (Fig. 1), which
May
June
July
increases the proFig. 1. Seasonal change of feeding sites of Grayportion of insects
faced Buzzards in Satoyama of Chiba Pref..
in their diet. They
Modified from Azuma (2004).
change their feeding sites to forage for seasonally most available prey.

Topics of ecology, behavior and conservation● Factors regulating the northernmost limits of thebreeding range

バードリサーチ生態図鑑
understanding the relationship between the competing sympatricspecies.
Grey-faced Buzzards were designated as a "Vulnerable" species in
December 2006 in Japan. Few concrete protective measures havebeen taken, however, partly because about 90% of the breeding
grounds are privately owned and 75% are not legally protected forwildlife. A basic plan for "Creating a wood Grey-faced Buzzards
can live" by Toyota City of Aichi Pref. (Ohata et al. 2006) is remarkable. In the Toyota Natural Observation Woods which contain a Satoyama landscape with Yatsuda, Toyota City has taken theinitiative in creating the habitat of frogs Gray-faced Buzzards preyon and maintaining their foraging grounds by weeding and water
management of private fallow rice fields. The conservation ofbirds of prey with a large home range, such as Grey-faced Buzzards would be promoted by the active involvement of local andregional governments in maintaining an entire local ecosystem
including private land in various regions of Japan.

Literature
Azuma A. 2004. Grey-faced Buzzard and regional ecological research on themaintenance of habitat. Abiko City Bird Museum Research Report Vol. 12:1119. [J]del Hoyo J., Elliott A. & Sargatal J. (eds.). 1994. Handbook of the Birds of theWorld. Vol. 2. New World Vultures to Guineafowl. Lynx Edicions, Barcelona.
Kojima Y. 1982. Territory and territorial behavior of the Grey-faced Buzzard(Butastur indicus). Tori 30:117-147. [J+E]
Kojima Y. 1987. Breeding success of the Gray-fased Buzzerd Eagle Butastue
indicus. Jap. J. Ornithol. 36:71-78.
Kojima Y. 1999. Nest Site Characteristics of the Gray-fased Buzzerd Butastue
indicus. Jap. J. Ornithol. 48:151-155.
Kumagai T., Tahara I. & Azuma A. 2006. On the distribution and the factors limiting the breeding in its northern limit region of the Grey-faced buzzard. - Insightfrom a preparatory survey- Summary of Ornithological Society of Japan annual
meeting in 2006: 80. [J]Maezawa A. 1990. Breeding case of two Grey-faced Buzzard males. Strix 9:225229. [J+E]
Matsuura T., Yokohari M. & Azuma A. 2005. Identification of potential habitats ofgray-faced buzzard in yatsu landscapes by digital elevation models and digitized
vegetation data. Landscape Urban Planning 70:231-243.
Momose H., Ueta M., Fujiwara N., Uchiyama T., Ishizaka T., Morisaki K. &Matsue M. 2005. Factor affecting the number of breeding Grey-faced BuzzardEagles Butastur indicus. Journal of the Japanese Institute of Landscape Architecture 68(5):555-558. [J+E]
Morioka T., Kanouchi T., Kawada T. & Yamagata N. 1995. Hawks and eagles ofJapan. Picture book. Bun-ichi Sogo Pub., Tokyo. [J]Nonaka J., & Nagano D. 2006. Breeding success of the Grey-faced Buzzard(Butastur indicus) in east part of Tochigi Prefecture and the moving range of thefledglings. Summary of Ornithological Society of Japan annual meeting in 2006:
79. [J]
Oh-hata K., Tejima Y., Hashimoto H. & Niizuma Y. 2006. Activity of the Woodsof Toyota-city natural observation concerning forest-making for the the Greyfaced Buzzard to inhabit. Annual meeting of the Wildlife Conservation Society
No. 12. (Okinawa). [J]● To prevent further decline

Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

frog population

It is assumed that the northernmost range of breeding Gray-faced
Buzzards is in Iwate and Akita Prefectures in Japan. In Akita Pref.
in the Japan Sea side, however, they breed in Noshiro at a higher
latitude (40°1' N) than Morioka (39°4' N) of Iwate Pref. in thePacific Ocean side where they are not confirmed to breed. This isprobably because the cold northeast monsoon called "Yamase"decreases temperatures in early summer in Iwate Pref., which inturn delays the emergence of, or reduces the supplies of prey animals, such as amphibians, reptiles and insects. Research showedthat the population of a dominant frog species (Rana porosa) inYatsuda of Iwate Pref. was100
Hanamaki(breeding area)significantly larger in theTamayama
Hanamaki region (39°2' N)
80(non-breeding area)SD
where Gray-faced Buzzards
Shizukuishi(non-breeding area)60
bred in a relatively high density than in the Morioka area
40
where they were not confirmed to breed (Fig. 2;
20Kumagai et al. 2006). In0
depth ecological studies ofnorthernmost breeding GrayEarly June
Late June
Early July
faced Buzzards are needed in
the future to determine their Fig. 2. Seasonal change of the mean
population of frog (Rana porosa)
breeding requirements as
in Satoyama of Iwate Pref. The
well as the limiting factors oferror bar = SDtheir breeding distribution.

Long-term counts of migrating Gray-faced Buzzards in some of
their stopover sites show that they have been declining rapidly inJapan. The population decline can be attributed to development in
the breeding grounds of Japan as well as deforestation and poaching in the wintering grounds of Southeast Asia. It is assumed to beimportant to Gray-faced Buzzards that their breeding grounds havea valley landscape and the boundary between a rice field andwoodland is long per area (Matsuura et al. 2005, Momose et al.
2005). This type of environment is usually used as Yatsuda inJapan, but Yatsuda tends to be consolidated or abandoned because
it is low in rice productivity. Both consolidation and abandonment
reduce the supplies of Gray-faced Buzzard prey animals, such as
frogs and snakes and deteriorate their feeding habitat, which inturn makes Yatsuda unsuitable for their breeding. In Saitama Pref.,central Japan, on the other hand, Gray-faced Buzzards have been
displaced from their breeding grounds by Northern Goshawks(Hiroshi Uchida pers. comm.), which suggests the necessity ofAuthor
Atsuki AZUMALaboratory of Conservation Biology
Faculty of Agriculture，Iwate University
I have resumed the ecological study of
Grey-faced Buzzards in Iwate Pref.
that is the northern limit of their breeding habitat. This time not alone but
together with my students. I would
like to make use of the study of Grayfaced Buzzards breeding in their
northernmost range to conserve theirhabitat as well as to determine thelimiting factors of their breeding.
azuma@iwate-u.ac.jp

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