Bird Research News

Vol.7 No.10

Japanese (Grey) Thrush
Morphology and classification
Classification: Passeriformes Muscicapidae
Total length:210-225mm
Wing length:♂ 111.3 ± 2.9mm (n = 60) ♀ 108.9 ± 3.1mm (47)
Tail length:♂ 75.7 ± 2.8mm (60)
♀ 72.4 ± 2.4mm (48)
Culmen length: ♂ 20.7 ± 1.0mm (62)
♀ 20.3 ± 3.1mm (50)
Tarsus length: ♂ 30.6 ± 0.9mm (62)
♀ 29.9 ± 1.2mm (51)Weight:50-65g (There is a record of a female of 83.0g in early November. )Total length after Clement (2000), the other measurements after the banding record(mean ± SD) in Kanazawa City in Ishikawa Prefecture by the author.

2010.10.19.

Kuro-Tsugumi (Jpn) Turdus cardis
mountains at an elevation of 300-1500
m above sea level. Outside of Japan,
on the other hand, they are assumed tobreed in the inland area of Chinesecontinent (Yamashina 1981). They
winter primarily from southern China
to the northern part of the Indo-China
Peninsula.

Habitat:
They breed in open woodlands as well as broad-leaved forests andconifer plantations. However, the breeding density varies greatlybetween similar-looking forests.

Appearance:
Japanese Thrush males are black on theupperpart and from the head to the chest.
The head is sometimes clearly distinguished from the back, which is tinged
with gray, but the difference is not readily discernible in a dark wood. The abdomen is scattered with black triangularflecks on a white ground. The bill and anarea around the eye are yellow. Females
are ocher on the upperpart and in theface. They are white from the throat tothe abdomen with brownish black andorange flecks. Some young males are
similar in plumage coloration to females.
On rare occasions, females may havedark gray upperpart that look remarkably
similar to young males.

Vocalization:

Life history
1whistle part

frequency (kHz)

Btrill part
B

B

abccd

10
50

2 seconds

phrase

34

5

6

7

8

breeding period910

11 12migration

Breeding system:

Photo 1. Adult JapaneseThrush male (above)and female (middle).
The female with a grayupperpart (below) had
a brood patch in theabdomen and there wasno change in plumage
coloration over time.

Fig. 1. Sonagram of atypical full song.
The same letter of
the alphabet represents the same typeof phrase.

Distribution and Habitat
Distribution:
Japanese Thrushes breed throughout Japan. They also breed in theforests of lowlands north of the Hokuriku region, central Japan,
but they generally breed in the woods of hills and42wintering
periodJapanese Thrushes call "Kyott" in a low
voice and utter "Dzee" when flying. They
call "Tsooo" or "Heee" intermittently in a thin high-pitched voice
when predators approach the nest.
A full song (complete song) lasts for 2-4 seconds at a time. It isdivided into the first and second halves, which are called a "whistlepart" and a "trill part", respectively. But the trill part is often omitted. One bird has about 20 types of phrases in a whistle part. Some
whistle parts consist of one phrase, such as "Kik-koke-kikk" andothers are composed of the same phrase repeated 2-4 times, such as"Kiyoko, kiyoko, kiyoko". Two or more types of phrases may be
used in one whistle part (Ishizuka 2006). A trill is a muttering note,such as "Tsrrin", "Tspiee, tspiee" and "Jijee", which is calleda"twitter part" in Common Blackbirds Turdus merula (Dabelsteen1984). One bird has about 70 types of phrases. Japanese Thrushes
sometimes continue trills for several minutes consecutively when
they (whether males or females) are close together, which suggeststhat trills play a major role in territorial defense and pair formation(Ishizuka 2006, Ishizuka 2008). Incidentally, caution is required
when you distinguish Japanese Thrushes and Grey-backed Thrushes(Turdus hortulorum) in spring in the regions along the Sea of Japanbecause the two species are strikingly similar in both call and song(Ishizuka & Tei 2004).
A

Photo 2. Nesting environment with abundantvines.

Japanese Thrushes mostly return to the breeding grounds in late
April, though it is not uncommon for them to arrive in the breeding sites around April 10 in central Japan. Single males sing in an
open wood or at the edge of a forest all day long. However, theystop singing to guard their partner immediately after they havepaired. The species is generally a monogamous breeder, but somemales breed with two females (Ishizuka 2009b).

Nest:Females start to build a nest in thewoods with a thick bush layer in late
April, while males move their songrange from a forest edge to a forestinterior. They prefer as a nest site thebase of a dead branch covered withvines and climbing plants, such as Akebi (Akebiae Caulis), Japanese honeysuckle (Lonicera japonica) and multi- Photo 3. Nest built on anartificial structure.
flora rose. They build a nest at a heightof 1.7m on average above the ground,but they occasionally nest in a conifer canopy 5-10m in height aswell. They build a cup-shaped nest using dead grass stems androots and mixing some mud with them. Most nests have mosses
attached on the outside. The nest is about 140mm in diameter andabout 50mm in depth.

Eggs, incubation and nestling periods and fledging rate:
The clutch size is mostly four eggs. The egg is scattered with reddish brown flecks on a pale blue ground. Females alone incubate
eggs and nestlings. The incubation period is about 13 days. Males
feed nestlings more than six times out of ten and tend to deliver alarger amount of food (a greater number of earthworms) to the nest
at a time as well. Nestlings fledge about 12 days after hatching.
Females begin to build a nest again 2-7 days after the nestlings
have fledged. Some pairs fledge their nestlings successfully threetimes in one breeding season. (Miyazawa 1971). Japanese Thrushes usually breed until August. Most of them leave the breeding
grounds in October and last birds usually in early November, butsome birds exceptionally winter in Japan.

Diet and foraging behavior
Japanese Thrushes generally forage for insects, chilopods andearthworms on the ground, but occasionally capture flying insects
in the treetops. They also eat the fruits of ivy (Hedera rhombea),
honeysuckle (Lonicera morrowii) and cherry. They primarily feedearthworms to nestlings.

♪ http://www.bird-research.jp/1_shiryo/koe/kurotsugumi_060604_okutadami_mju.mp3 ♪ http://www.bird-research.jp/1_shiryo/koe/kurotsugumi_0804_hyogo_kaji.mp3
Mutsuyuki Ueta

Kyoko Kajimoto

Bird Research News

Vol.7 No.10

2010.10.19.

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

バードリサーチ生態図鑑

Topics of ecology, behavior and conservation● Repertoire of songs and the number acquired females

number of trill types

There is no correlation between the variety of whistles or trills andthe age or Japanese Thrush males. However, a male breeding with
two females tended to have more various trills than a monogamous
male breeder, while there was no difference in the variety of whistles between the two types of male breeders (Ishizuka 2009a).
6040
number ofacquired females

20●2001020●130

number of whistle types○040Fig. 2. Relationship between thenumber of types of whistles
and trills and the number ofacquired females in 17males. The number of trill
types is the number extracted from the 110 full songsof each male.

● Differences in song between single and mated males
Single males sing loudly at short intervals on top of a tree. They
tend to add trills to their songs and change their types in rapid
succession. Full songs represent 60-100% of the singing frequency. Mated males generally sing in a relatively quiet voice in a tree
crown, however, because they sing in the vicinity (usually within30m) of their partner or nest. They sing at long intervals and often
omit trills, singing the same type of song repeatedly. Full songs
account for up to 50% of the singing frequency. Field experiments
can also show that there is a difference in the way of singing between mated and single males. For instance, mated males sing afull song with significantly higher frequency when their partner is
temporarily isolated from them (Ishizuka 2008). About 30 minutes
before sunrise, however, even mated males also sing all together inthe same way as single males do. Even in the daytime, on the other
hand, some mated males sing a song similar to that of single males
in areas relatively distant from the nest. Some males own two separate singing areas and sing songs, going from one area to another,
but their way of singing are different between the areas, if they
breed with their partner in one of the areas (Ishizuka 2009b).

● Predawn singing excursion
Males sometimes sing at a distance of 300m-1000m from the nest
before dawn. The faraway singing area of one male overlaps withthat of another male, but they do not sing close to each other.
Though another male sometimes silently approaches up to 1 or 2mfrom a singing male, the singing male usually do not chase himaway. In addition, these singing males hardly ever show any reaction (territorial defense behavior) to the replayed songs of othermales. This experiment suggests that the main purpose of singing
far away from the nest is to attract the second female, but not todefend the territory. Since females are aggressively intolerant ofeach other, it is assumed that males have adopted a strategy to singin areas distant from the nest to attract and acquire two or more
females (Ishizuka in press).

● Case of the extinction of a local breeding population
In the seaboard of Kanazawa City, Ishikawa Prefecture, JapaneseThrushes used as a nest site a shelterbelt composed primarily of Japanese black pines (Pinus thunbergii) and Robinia pseudoacacia in awooded park. They usually nested in a site where a slanting dead tree
leaned against another tree. Such a site was densely covered withvines as well. When the bush layer, vines, weeds on the forest floor
and dead trees were removed as a part of the park management, theirbreeding habitat was not only deteriorated but the nests were also
vulnerable to the predation of natural enemies, such as crows.
The motorway that runs through the woods opened around 2000. The
area where Japanese Thrushes nested with high density was converted into mallet golf courses, and the forest floor was further cleared.
The water vein of the dune was managed and the environment wassimplified. Moorhen (Gallinula chloropus), Brown Shrike (Laniuscristatus) and Great Reed Warbler (Acrocephalus orientalis) ceased
to breed. More than 30 pairs of Japanese Thrushes breeding there in
the 1990s sharply declined and they have vanished since 2007.
It is assumed, one the other hand, that Japanese Thrushes were intermittently distributed along the seaboard from the base of the Noto
Peninsula to Kanazawa City. There is also a possibility, however,that they began to decline around 1990 from the northeastern area
toward the southwest. Since they also declined in some areas withalmost no artificial modification, it is still unknown what caused
them to vanish from these breeding grounds. Brown Shrikes andJapanese Thrushes seemed to decline in the similar habitat of Niigata
City in the 1990s as well.

Literature
Clement P. 2000. Thrushes. Princeton University Press. Princeton, New Jersey.
Dabelsteen T. 1984. An analysis of the full song of the Blackbird Turdus merulawith respect to message coding and adaptations for acoustic communication.
Ornis Scand. 15:227-239.
Ishizuka T. & Tei S. 2004. Initial breeding behavior of the Grey-headed Thrush.
Strix 22:201-206. [J+E]
Ishizuka T. 2006. Song structure and repertoire of Japanese thrush (Turdus cardis)
and the effectiveness of individual identification by song. J. Yamashina Inst.
Ornithol. 37:113-136. [J+E]
Ishizuka T. 2008. Changes in song structure and singing pattern of the Grey Thrush
Turdus cardis as responses to song playback and mate removal experiments.
Ornithol. Sci. 7:157-161.
Ishizuka T. 2009a. Repertoire sizes of the whistle and trill parts of the song of theGrey Thrush Turdus cardis in relation to the mating success of the males. J.
Yamashina Inst. Ornithol. 40:83-89.
Ishizuka T. 2009b. Singing behavior in polygynous Grey Thrush Turdus cardis
males. Ornithol. Sci. 8:87-90.
Ishizuka T. 2009c. Whisper song in the Grey Thrush Turdus cardis immediately
before and after feeding their young. J. Yamashina Inst. Ornithol. 41:34-41.
Ishizuka T. In press. Dawn trips made by the male Grey Thrush Turdus cardis tosearch for a second mate. Ornithol. Sci. 9.
Miyazawa K. 1971. The life history of the Japanese Thrush: Life of the breeding
period. J. Yamashina Inst. Ornithol. 6: 300-315. [J+E]
Yamashina Y. 1981. Japanese birds and their ecology (Reprint: Vol. 2). Shuppankagaku sogo-kenkyujo. [J]Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

AuthorToru ISHIZUKA The Biodiversity Laboratory Earthworm● Soft whisper song
Males make soft whispering once or twice before and after feeding
nestlings. Some males whisper more frequently just before they
deliver food to the nest when females brood nestlings in it. Females leave the nest on hearing their whispers. On the other hand,males tend to whisper more often after leaving the nest when females are not present in the vicinity. Cases are on record wheremales whispered frequently when nestlings fledged (Ishizuka
2009c).

I am currently engaged in the habitat conservation of Latham's Snipes and Chestnutcheeked Starlings in my hometown of
Karuizawa, Nagano Pref., worrying aboutincreasing alien Hwamei (Garrulax canorus).
I have been monitoring the "Reduced habitats" of insects, fish and amphibians as well. I
have written "Interesting private life of birds","Forests have complicated reasons to be thisway", etc.

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