23

Invasion by White-browed Laughing Thrushes (Garrulax sannio)
into Central Japan
Hitoshi TOJO1, Kazuko OSAWA2, Hiroshi TERAUCHI3, Manabu KAJITA4,
Amane KAJITA5 and Osamu WATANUKI61

Wildlife Ecology Laboratory, Forestry and Forest Products Research Institute
P.O. Box 16, Tsukuba Norin, Ibaraki 305-8687, Japane-mail: tojo@ffpri.affrc.go.jp
2
Kiribara 692-4, Omama Town, Yamada-gun, Gunma 376-0102, Japan3
3-7-15 Miyamoto-cho, Kiryu City, Gunma 376-0056, Japan
4
Department of Zoology, Graduate School of Science, Kyoto University
Kyoto 606-8502, Japan.
5
Kitafunaoka-cho 49, Murasakino, Kita-ku,, Kyoto City, Kyoto 603-8227, Japan.
6
Gunma Museum of Natural History
1674-1 Kamikuroiwa, Tomioka City, Gunma 370-2345, Japan.

Abstract
The exotic White-browed Laughing Thrush (Garrulax sannio) has been recorded in Gunma
Prefecture, central Japan, since the 1990s. We studied the distribution of this alien species, caught one
individual in 2000, and found an active nest in 2001. The recorded observations were all in thesoutheastern region of Gunma Prefecture, except for one in Ibaraki Prefecture. The earliest record wasmade in 1994, as far as we know. So far, the Laughing Thrushes in Japan have been found in
human-modified habitats such as secondary forests, bamboo thickets, cultivated fields, and residential
areas. Because such habitats are common in rural areas of Japan, the White-browed Laughing Thrush
seems to have no difficulty in expanding its region and may present problems regarding conservation of
biological diversity in those areas.
Key words: Garrulax sannio, introduced species, invasive species, White-browed Laughing Thrush

1. Introduction
The family Timaliidae, the babblers, comprises
more than 200 species, distributed for the most part inIndo-Malayan Asia and Africa (Cibois, 2003). Although no native babbler species breed in Japan(Ornithological Society of Japan, 2000), three species,
the Red-billed Leiothrix, Leiothrix lutea (Eguchi &Masuda, 1994; Tojo, 1994), the Masked Laughing
Thrush, Garrulax perspicillatus (Nakamura et al.,1993), and the Hwamei, G. canorus (Sato, 2000), haveinvaded during the past two or three decades.
Biological invasion is one of the most serious
threats to the conservation of native biodiversity, andinvasion of alien birds can also cause various economic and ecological problems (Lever, 1994; Holmes& Simons, 1996; Tojo, 1996; Eguchi & Amano, 1999,
2000). Unlike most introduced bird species that
prefer human-modified habitats, these babblers may
penetrate deep into forests.
For example, theRed-billed Leiothrix and the Hwamei have invaded
natural forests on the Hawaiian Islands, where they
Global Environmental Research8(1)/2004: 23-28
printed in Japan

appear to compete with native bird species. Mountainspring and Scott (1985) explored passerine bird
associations in the forests of Hawaii and found thatnative–exotic species pairs had a significantly greater
proportion of negative partial correlations than either
native–native pairs or exotic–exotic pairs. In Japan,
the Red-billed Leiothrix has invaded natural deciduous forests (Eguchi & Masuda, 1994; Tojo &Nakamura, 2004). Babblers are therefore a groupwhose potential for invasion needs careful monitoring.
The White-browed Laughing Thrush (Garrulax
sannio) is native to eastern, central and southern
China, Hainan Island, Tibet, eastern Assam, Myanmar,
Laos, Tonkin (de Shauensee, 1984) and northern
Thailand (Lekagul & Round, 1991). It was neverrecorded in Japan until recently (OrnithologicalSociety of Japan, 2000).
We determined the present distribution of theWhite-browed Laughing Thrush in Japan and alsostudied past records to clarify the initial stages ofinvasion and future problems this species may cause.
©2004 AIRIES24

H. TOJO et al.

2. Study Area and Methods
The area where White-browed Laughing Thrushes
have been observed is in the southeastern part ofGunma Prefecture (e.g., Shiono, 1994; Osawa, 1997
and 1998; Maebashi City, 1999). This area is on thenorthwestern edge of the Kanto Plain and is surrounded by mountain ranges (including Mt. Akagi,
1,828 m) to the north and west. Although this area
includes Maebashi City, the capital of Gunma Prefecture, most of the land is used for agriculture andincludes rice paddies, mulberry groves, cultivatedfields, secondary woods and bamboo thickets as well
as residential areas.
We made observations of the Laughing Thrush
from 1999 to 2001. Two of us live in the target areaand had the opportunity to observe Laughing Thrushes
in daily life while also gathering information fromother persons. Although many photographs of theWhite-browed Laughing Thrush had been taken, nobirds had been captured and examined in Japan. We
thus captured a bird to verify the species identification.
We also searched for active nests for evidence of
breeding and to investigate the birds’ breeding
ecology.
In addition, we searched for recorded observationsof the species in resources such as local newspapers
and newsletters of the Gunma branch of the Wild Bird
Society of Japan. We examined these materials fordetails on past sightings of the species. When possible, we contacted the original observers for additional details.

dential lot surrounded by houses, a road, and agraveyard with a small grove. A White-browed
Laughing Thrush was sitting on the nest when we discovered it. The nest was set on bamboo stems (Fig.
2(a)) and contained two nestlings and two eggs (Fig.
2(b)). The eggs were pale blue and measured 26.2 ×
20.0 mm and 26.5 × 19.7 mm. These characters are
consistent with those described by Cheng (1987).
The dimensions of the nest (Table 2) also were consistent with the range of those measured in China (Cheng,1987). When we visited the nest again on May 2, thetwo unhatched eggs remained. The two nestlings
had grown and were measured and banded (Fig. 2(c)).

(a)

3. Results
3.1 Capture and breeding records
On March 18, 2000, we caught a White-browed
Laughing Thrush in a mist net in a stand of bamboo in
Ogo Town (Fig. 1(a)). All measurements of the bird
(Table 1) were within the range for White-browed
Laughing Thrushes in China (Cheng, 1987). The
bird’s short, rounded wings (Fig. 1(b)) suggest that it
is not good at long-distance flight. We attached ametal number ring to the bird before releasing it, thefirst banding of this species in Japan.
We found an active nest in a residential area inKasakake Town on April 25, 2001. The nest site wasin a clump of bamboo (Pleioblastus chino) in a resiTable 1(b)Fig. 1A White-browed Laughing Thrush captured on March
18, 2000. (a) Overall view of the bird; (b) view of its
rounded wing and long tail.

Measurements of White-browed Laughing Thrushes captured in Japan and China.

Location

Sex

Natural Wing (mm)Tail (mm)Tarsus (mm)Exposed Culmen (mm) Total Length (mm) Body Weight (g)Gunma, Japan unknown

94.3

106.4

35.8

20.7

235

61

China

males (20)

96.5 (91.5-99.5)

108.8 (98-115.5)

38 (36-39)

21 (19-22)

228 (210-255)

67.5 (60.5-78)(Cheng1987)

females (20) 93 (90-98)

104 (97.5-111.5)

37 (35-39)

20.6 (19.5-22.5)

215 (108*-234)

65 (57-70)*Assumed to be a typographical error for 208.

White-browed Laughing Thrush in Japan

25

(a)

(b)
Fig. 2(c)
A White-browed Laughing Thrush nest in Kasakake Town, Gunma Prefecture. (a) Nest set among bamboo stems on April
25, 2001; (b) nestlings and eggs in the nest on April 25, 2001; (c) a nestling on May 2, 2001.

Table 2

Measurements of nests in Japan and China.

Location

Ext. diam. (cm)Int. diam. (cm)Ext. depth (cm)Int. depth (cm)Gunma, Japan

17.4 × 13.3

9.8 × 7.6

10.7

5.5

China (10 nests, Cheng 1987)

13.8 (11-20) × 11.4 (7.5-14) 8 (6-9.5) × 8 (6-9)

9.8 (8-12)

6 (4-9.2)

3.2 Distribution and habitats
During 1999–2001, we observed Laughing
Thrushes at about 30 sites, including the capture site
and the nesting site described above. We mapped
our observations and those of others (Fig. 3). Laughing Thrushes were observed all year round and thus
appeared to be residential, a characteristic of babblers(Campbell & Lack, 1985). Most recorded observations were of two to several birds, although determining the exact number of birds was difficult
because they tend to live in the underbrush.
The earliest record that we could find was a photograph taken in Maebashi City in the spring of 1994
(Shiono, 1994). In 1996, Laughing Thrushes wereobserved over a wide area. In March 1996, one
White-browed Laughing Thrush was seen in a residential area in Kiryu City (C. Miyazaki, personalcommunication). In the autumn of 1996, 5–6 birds
were observed in the border area between Omama
Town and Niisato Village, and in February, March,
and April 1997, 2–6 birds were repeatedly observed inthis area. An observation was also recorded in
Maebashi City in December 1996 (Osawa, 1997). In
1998, records of White-browed Laughing Thrush became common in Omama Town, including its residential areas, indicating an increased population(Osawa, 1998). In Maebashi City, White-browed
Laughing Thrushes were recorded in four out of 17
census plots for a survey on the natural environment
conducted from August 1997 to May 1998 (Maebashi
City, 1999).
Outside Gunma Prefecture, we could find only one
observation site, in Iwai City, Ibaraki Prefecture.
One bird was observed on February 2, 1997, on April

26

H. TOJO et al.

Fig. 3Distribution of recorded observations of the White-browed Laughing Thrush. The first year ofobservation at each point is shown. The mapped points include reports of observations in
Maebashi City (1999), Osawa (1997, 1998), and Shiono (1994).

4 and May 2, 1999, and on March 5, 2000, and two
birds carrying nest materials were observed on April
27, 1999 (M. Hatori, personal communication withphotographs). So far, there is no evidence for successful breeding and establishment of a stable population in Ibaraki.
Habitats in which White-browed Laughing
Thrushes were observed were secondary forests, especially those with a bamboo understory, abandoned
mulberry groves, cultivated fields, parks, and residential gardens. In Maebashi City, habitat types inwhich White-browed Laughing Thrushes occurred
included broad-leaved woods, pine woods, and cultivated fields (Maebashi City, 1999). In a home garden in a residential area of Omama Town, Laughing
Thrushes were observed almost every day after thespring of 1998 (Osawa 1998).

4. Discussion
From the morphological traits of birds and eggs,
there remains no doubt that the exotic bird observed inJapan is the White-browed Laughing Thrush. Considering the bird’s strict residential nature in its native
range and its wing morphology, it seems unlikely thatit invaded Japan by itself. The population in central
Japan, therefore, appears to derive from birds thatwere imported and released, whether accidentally ordeliberately.
The earliest record of a White-browed Laughing
Thrush that we could find was in 1994. The initial

release, however, could have been much earlier than
1994, as our results showed that this species was
widely distributed by 1997–1998 (Fig. 3).
The
Laughing Thrush is now widely distributed in thesoutheastern part of Gunma Prefecture, between theTone and Watarase rivers, about 80–500 m above sea
level. If our study area was not broad enough, thismay well prove to be only part of the range.
The sightings in Ibaraki Prefecture (about 60 km
from the area in Gunma Pref.) indicate that
long-distance dispersion of this species might occur.
The birds observed in Ibaraki Prefecture might have
moved along the Tone River from Gunma to Ibaraki.
Although no evidence for their establishment in
Ibaraki was found, such movement can result inpioneer populations in new areas.
The Laughing Thrush in the study area utilized
secondary forests, bamboo thickets, cultivated fields,
and residential areas as its main habitats. The preferred habitats of this species in its native areas aresecondary forests, bamboo thickets, scrub, grasslands
and forest edges (Swinhoe, 1867; de Shauensee, 1984;
Lekagul & Round, 1991; Robson, 2000), which aresimilar to its habitats in Japan. Such habitats arequite common in rural areas of Japan and are probably
increasing because of poor management of secondary
forests, and neglect of mulberry groves formerly used
for sericulture. As this species can nest in bamboo, it
is unlikely that a shortage of nesting sites will limit
the population size. The Red-billed Leiothrix, which
nests in dwarf bamboo (Sasamorpha borealis), has

White-browed Laughing Thrush in Japan

reached very high densities in Japanese forests into
which it has penetrated (Amano & Eguchi, 2000; Tojo
& Nakamura, 2004). Economic damage to agricultural products may occur if the Laughing Thrush becomes dominant, as it is reputedly a pest of crops,
fruits orchards in Thailand (Lekagul & Round, 1991).
Because no natural forests occur within the present
range of the White-browed Laughing Thrush in Japan,
it is difficult to predict how it may penetrate natural
Japanese forests, remnants of which exist mainly athigh altitudes. This species is normally distributed in
mountainous areas in its native range (Deignan, 1952;
de Shauensee, 1984; Viney & Phillipps, 1988;
Lekagul & Round, 1991; MacKinnon & Phillipps,
2000; Robson, 2000), so the harsh climate of highaltitudes may not prevent invasion by this species inJapan. However, this species may actually preferhuman-modified habitats to natural forests. The
residential nature of the species may also have slowed
expansion of its range into surrounding mountainous
areas.
White-browed Laughing Thrushes may pose a
problem regarding conservation of biological diversity
in rural areas, one important conservation issue
recently in Japan. The traditional rural landscape ofJapan (called SATOYAMA) has been abandoned or
destroyed by regional development projects, especially during the recent 30–40 years (Washitani 2001,
Takeuchi et al. 2003) and many bird species once
common in such a habitat have become rare and somehave been red-listed (Ministry of the Environment,
Japan, 2002). We suggest that the abandonment of
secondary forests and mulberry fields has provided
good habitats for Laughing Thrushes and the increaseof such exotic bird species will have additional negative effect on declining native bird species throughcompetition or nest predation. Monitoring surveys ofbird communities in areas where Laughing Thrushes
are increasing are necessary for detecting thoseeffects.
On the other hand, competition among exotic bird
species in such habitats was suggested in Hawaii(Moulton & Pimm, 1983; Moulton, 1993). Because
the Hwamei’s range has expanded into areas
neighboring that of the White-browed Laughing
Thrush in Japan, competition between these two
exotic birds may arise and affect the expansion of
their respective distribution ranges.

Acknowledgements
We greatly appreciate the help of H. Takeuchi of
the Omama Town Museum; Y. Machida, J. Miida, Y.
Kitakaze, T. Hasemi, K. Yamaga of the Kiryu Nature
Sanctuary; M. Fujii and Y. Odagiri of Maebashi City;
and Y. Abe, T. Akuzawa, M. Ebara, M. Fujikake, N.
Fukai, M. Kanaya, N. Hashimoto, M. Hatori, Y.
Iwashita, A. Iwata, C. Miyazaki, S. Shibata, M.

27

Shiono and K. Tanaka for information on the Laughing Thrushes. This research was partly supported by
the Ministry of the Environment, Japan (Global
Environmental Research Fund, project leader: K.
Goka).
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