Vol.3 No.6

Bull-headed Shrike

2006. 6.19.

Mozu (Jpn) Lanius bucephalus

Morphology and classification
Classification: Passeriformes Lanidae
Bull-headed Shrikes are classified into two subspecies of L. b.
bucephalus (Japan) and L. b. cicarius (China). It is said that in L.
b. cicarius the bill is black from the tip to base, and the upperpartis darker in males than in females. Wave-shaped specks on theflank are distinct in females.
Total length:
Wing length:
Tail length:
Culmen length:
Tarsus length:
Weight:20.1cm (18.5-21.2)♂ 84.6mm (80.7-89.5)♂ 88.4mm (79.6-96.0)♂ 16.4mm (14.4-18.7)♂ 26.1mm (24.2-28.3)♂ 40g (35-46)♀ 83.5mm (80.2-88.4)♀ 85.5mm (79.4-93.4)♀ 16.2mm (13.8-17.8)♀ 26.1mm (24.1-27.8)♀ 41g (34-52)

Total length after Enomoto (1941) and the others are the mean (range) measured in
the breeding period in the Ishikari region of Hokkaido.

Appearance:
Bull-headed Shrikes have distinct dimorphism
which is rare in true shrikes. A black eye stripe, agray back and a white patch at the base of primary flight feathers characterizemales. In females, on the otherhand, the eye stripe is darkbrown and the wave-shaped
speckles from the flank to thebelly are more distinct than inmales. There is no white patch Photo 1. Male
Bull-headedin the primary flight feathers. ItShrike.
is possible to distinguish be[H.Nagashima]
Photo 2. Female tween one-year-old birds (withBull-headedflecks) and birds of more than one year oldShrike.
(fleckless), based on brown flecks at the tip of[H.Uchida]proximal primary wing coverts.

Vocalization:
In the breeding period, Bull-headed Shrikes advertise their territory,calling "Gyun, gyun" at the top of a tall tree and a utility pole. Theysing a "subsong", mimicking the songs of other bird species, such as
Brown-headed Thrush, Oriental Greenfinch, Japanese White-eye,Brown-eared Bulbul, and Latham's Snipe. But Bull-headed Shrikes
cannot faithfully reproduce their vocalization. In autumn they utter"Kich-kich-kich" continuously in a high-pitched voice to claim theirwinter territory, which is called "Takanaki (high-pitched singing)"
and familiar to Japanese people as a special feature of autumn.

Distribution and Habitat
Distribution:
Bull-headed Shrikes breed in southern Sakhalin Island, the seaboardof the Japan Sea from Primorsky Province of Russia to the Korean
Peninsula, the coastal area of the Yellow Sea and Japan. In Japanthey breed from Hokkaido to Kyushu including small islands aroundthe mainland, such as the Izu Islands, Chichijima of the Bonin Islands, Nakanoshima, Kikaijima, Minami-daitojima and Kitadaitojima. In the Nansei Islands south of the Ryukyu Islands, however, they are not confirmed to breed. Though the breeding population in the northern regions moves to the south in winter, some birds
still remain in the suburbs of Sapporo, Hokkaido in midwinter. They
started to breed in the two Daitojima Islands and Chichijima Islandin the 1970s and the 1980s, respectively and have increased in number.

Habitat:Bull-headed Shrikes prefer open habitats, such as farmland, meadows, riverbeds and suburban parks. They breed in habitats withshrubs and hedges. Electric wires, fences and forest edg-es play an important role as a perching post in foraging. The homerange in the breeding period varies depending on the distribution ofperching posts, ranging from 1 to 4ha. They breed at an elevation of
0-1,800m (asl) in central Honshu (the largest main island). They
usually begin to breed in late February and fledglings become independent by May in the lowlands of Honshu, where they leave thebreeding grounds when they have finished breeding. In highlands,
on the other hand, they start to breed in May. There is a theory that
Bull-headed Shrikes breed once again in highlands after the firstbreeding attempt in lowlands because the departure from the lowland breeding grounds corresponds to the breeding start in highlands.

Life history
123 4 5 6 7 8 9 10 11 12breeding in breeding in non-breeding season
the lowland the plateau

Breeding system:
Bull-headed Shrikes are monogamous breeders, but nestlings byextra-pair fertilization are confirmed in about 17% of the nests.

Nest:
The site and height of a nest varied according to available vegetationin the Ishikari region near Sapporo, Hokkaido. Bull-headed Shrikesprimarily used as a nesting plant Vitis coignetiae, Pleioblastus chino, Malus baccata and Hydrangea paniculata. They mostly built anest at a height of 86cm (range 30-279cm). In Minami-daito(-jima)Island, on the other hand, they built a bowl-like nest principally in
Calophyllum inophyllum and Garcinia spicata planted as a fieldpartition at a height of 252cm on average above the ground. They
made the exterior shoddily using grass leaves and stalks, but lined
the interior elaborately with ears of Miscanthus sinensis. The nest
was 10-15cm in outer diameter and 7-10cm in inside diameter witha depth of 5-8cm.

Egg:
The clutch size is 2-6 eggs,
but two- or three-egg clutches are rare. The most common clutch size varies between regions. For instance, Photo 3. Brown and red types of Bullheaded Shrike eggs
it is six eggs in the Ishikari
region and five eggs in Minami-daito Island. The clutch size also
varies depending on the season and the year. The mean egg size is
23.6mm (21.0-25.9mm) by 17.9mm (16.2-19.3mm). The egg isbrown with dark brown flecks more dense around the blunt end. It
rarely has reddish brown flecks on a reddish white ground (Photo 3).

Incubation and nestling periods:
Nestlings hatch 15 days after the last egg was laid. Eggs generally
hatch synchronously except for the last-laid egg, which hatches
one day later. The hatching rate is higher in the Ishikari region (ca.
95%) than in Minami-daito Island (ca. 70%). In Ishikari, however,the breeding success rate is as low as about 40% due to the nest
predation of red foxes
5(Vulpes vulpes), Japanese rat
4snakes (Elaphe climacopho3ra) and Large-billed Crows2(Corvusmacrorhynchos),1though this rate varies from0
one year to another. Once
0510152025eggs have survived predaprecipitation (mm)tion, their chances of fledging are improved, but the Fig. 1. Relationship between the number of nestlings that disappeared
mortality of nestlings rises asfrom the nest in the study site in a
rainfall increases in the nestlday and the precipitation from theing period (Fig. 1). In theprevious day. Lost nestlings arelate breeding period, someassumed to have died.
number of lost nestlings

Bird Research News

4

♪ http://www.bird-research.jp/1_shiryo/koe/mozu_1002_hyogo_kaji.mp3
Kyoko Kajimoto♪ http://www.bird-research.jp/1_shiryo/koe/mozu_081014_watarase_hirano.mp3
Toshiaki Hirano

Bird Research News

Vol.3 No.6

2006. 6.19.

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

バードリサーチ生態図鑑

nests are parasitized by Common Cuckoos (Cuculus canorus). The
breeding success varies from 20% to 50% depending on weather
and the density of predators.

Feeding ecology
Bull-headed Shrikes perch on a high place and stoop at beetles andspiders prowling on the ground in an open habitat. They may also
flycatch flying insects and snatch insects from leaves on the wing.
They depend heavily on orthopteran insects in Minami-daito Island. They occasionally capture small mammals and small birds
including even thrushes that are larger than themselves. They may
also eat fruits in winter when their staple food is in short supply.
They have a habit of keeping their captured prey impaled on athorn or barbed wire, which is called “Hayanie” (Photo. 5). The
habit of "Hayanie" peculiar to shrikes is assumed to have several
functions, such as caching against a food shortage and the sign of aterritory boundary. It is reported that Loggerhead Shrikes (Laniusludovicianus) keep a toxic grasshopPhoto 5.
per impaled on a thorn until detoxicat"Hayanie":
ed before ingesting it. It is also said
A Fejervarthat Loggerhead Shrike males withya frogmore pierced prey are at an advantage
impaled on awhen attracting a mate, which sugbarbed wire.
gests that "Hayanie" has an adaptive
value.

Topics of ecology, behavior and conservation● Does a clutch size depend on a male's ability?

Clutch size

Reproductive performance is generally
6.0
8
better in adult birds than in juveniles.
5.8 n=28
15Females play a major role in this age5.6
dependent breeding performance in
5.4
10
many bird species. In Bull-headed
5.2
Shrikes, however, juvenile females
5.0
paired with an adult male lay more
4.8
eggs than adult females paired with a4.6
juvenile male (Fig. 2). In other words,
Ad-M Ad-M Y-M Y-M
××××
the age of males has a greater effect on
Ad-F Y-F Ad-F Y-F
a clutch size than that of females in
Bull-headed Shrikes. In Bull-headed Fig. 2. Relationship between clutch size and theShrikes, the courtship feeding fromage structure of a Bullmales to females is concentrated fromheaded Shrike breeding
pre-egg laying to the egg-laying period.
pair. (Takagi 2003)
Courtship feeding generally occurs
from courtship to mating period. In Bull-headed Shrikes, however,courtship feeding is not followed by copulation, which suggeststhat the feeding serves as the nutritional supplementation of females. Since adult males fed their mate more frequently than juvenile males, females are assumed to receive an adequate supply ofnourishment. As a result, females paired with an adult male can lay
more eggs. In addition, adult males tended to feed larger items offood to the young in the nestling period. The result suggested that
Bull-headed Shrike females lay eggs depending on the availabilityof food that is assessed by the food-providing activity of pairedmale.

● How best to ensure paternity
Bull-headed Shrike nestlings near fledging open and shut theirwings repeatedly, calling "Gee, gee, gee" loudly when they beg
their parents for food. This behavior is called food-begging. Females also beg their mate for food in this way in the breeding period, but males sometimes show food-begging behavior as well.
Bull-headed Shrikes usually copulate in the early morning and theevening in the vicinity of the nest. Males show food-begging be-havior first, when their mate approaches them in response to thisbehavior and copulates. Copulation is repeated several times consecutively. After males were away from their mate for a while in
the pre-egg laying which can be the fertilization period, however,males sometimes copulate without food-begging behavior. I haveobserved this type of copulation in the egg-laying period. A maleterritory owner dashed about 150m toward a male intruder andchased him out of the territory in 30 seconds or so. And just afterthat the territorial male copulated with his mate without foodbegging behavior. It is possible to interpret this copulation without
food-begging behavior in terms of guaranteeing paternity. In Bullheaded Shrikes, extra-pair fertilization occurs at a rate of about
10%. In other bird species, females are inseminated with sperms
from the male they last copulate with, or when the copulation frequency is higher. If Bull-headed Shrike females are also inseminated with sperms from the last copulation, the purpose of urgent
copulation without ceremony would be to guarantee paternity.
When eggs fertilized through extra-pair copulation hatch, males
will feed the nestlings of a stranger male for more than 30 days.
Breeding efforts reduce the survival rate of breeders. In short,guaranteeing paternity can be important in terms of a life history
strategy.

Literature
Chiba H. 1990. Bull-headed Shrikes Breeding in Ogasawara Islands. Jpn. J. Ornithol. 38:150-151. [J+E]
Enomoto Y. 1941. Wild Bird Handbook (Vol. 2). Osaka Chapter, Wild Bird Society of Japan. [J]Imanishi S. 2005. Where did Bull-headed Shrikes in the plateau come from andwhere do they go?: On the movement of Bull-headed Shrikes. Birder 19 (10):3031. [J]Karasawa K. 1980. The story of the Bull-headed Shrike. Hokuryukan. [J]Matsui S. & Takagi M. 2005. The Bull-headed Shrike that moved to the subtropics
islands. Birder 19 (10):27-29. [J]Nishiumi I. 1997. Is the Bull-headed Shrike really monogamous?: Searching for thebreeding ecology of birds from DNA. Life magazine 17:12. [J]Ogawa I. 1977. Diet analysis of the Bull-headed Shrike from pellets and its seasonal changes. Tori 26:63-75. [J+E]
Takagi M. 1994. Territory behavior of the Bull-headed Shrike in the breeding
period. Birder 8 (9):24-27. [J]Takagi M. 2001. Some effects of inclement weather conditions on the survival andcondition of bull-headed shrike nestlings. Ecol. Res.16:55-63.
Takagi M. 2003. Different age-effects on reproductive performance in relation tothe breeding stage in Bull-headed Shrikes. J. Ethol. 21:9-14.
Takagi M. 2005. Chick-rearing strategy of the Bull-headed Shrike. Birder 19(10):24-26. [J]Yamagishi S. 1981. Marriage of the Bull-headed Shrike. Dainippontosho. [J]Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

Author
Masaoki TAKAGI

Graduate School of Science,Osaka City University

I started to study the life history of Bull-headed Shrikes in the Ishikari
region, Hokkaido. I have been still studying it from a long-term pointof view in Minami-daito Island, a subtropic oceanic island with mystudents. I will aim at the study that treats their life-long reproductive
success by pursuing the population dynamics. In addition, I am engaged in researches on the individual identification of a subspecies of
Ryukyu Scops Owls based on the vocalization as well as its mechanism for avoiding inbreeding in
Minami-daito Island. I would also
like to clarify the environmental
adaptation of the vocalization of
Ryukyu Scops Owls widely distributed in the Nansei Islands. I enjoy
fishing in my spare time.
mtakagi@sci.osaka-cu.ac.jp

5