Bird Research News

Vol.2 No.5

2005. 5.11. Last Revised:2014.4.10.

Japanese Pygmy Woodpecker
Morphology and classification
Classification: Piciformes Picidae
Total length:
Wing length:
Tail length:
Culmen length:
Tarsus length:
Weight:about 15cm
♂ 76-88mm♂ 42-57mm♂ 13.5-17.2mm♂ 13.4-15.7mm♂ 17.8-22.8g♀ 79-91mm♀ 46-57mm♀ 14.5-18.7mm♀ 13.7-16.3mm♀ 19.3-26.4g

Total length after Yoshii (ed. 1988), and other measurements taken by the author in
the breeding period in Japan. The measurements include individuals captured fromHokkaido to Okinawa. The body size tends to be smaller in the southern regions than
the northern ones from Sapporo, Hokkaido to Takachiho, Kyushu. The individuals ofAmami-Oshima and Okinawa Islands are smaller than those of Kyushu. The measurements suggest that the populations of small islands, such as Miyakejima of the Izu
Islands have morphological variation types different from those which the mainland
populations from Hokkaido to Kyushu show according to latitudes. The details areunder research.

Appearance:

90feather length (mm)

Kanto
Males and females are roughly
similar in plumage coloration. The80
back and wings have brownish gray
Okinawa
70and white flecks. The abdomen ismostly white with brownish verti60
cal stripes. The superciliary is distinctly white and the bill is black.
50
P9 P8 P7 P6 P5 P4 P3
Males have several red feathers on
Primary flight feather code
the side of the back of the head,
which can be invisible. In juveniles Fig. 1. Primary flight feather
lengths of the populations of
the tail is short, the edge of a bill is
the Kanto region and Okinatinged with yellow and plumage
wa Island. Primary flightflecks are not so evident as infeathers are P9 to P3 in orderadults.
from the outer of a wing.
The plumage coloration varies
between regions as in the morphology. Japanese Pygmy Woodpeckers tend to look darker in the southern regions than in thenorthern ones, such as Hokkaido because the areas of white decrease as they go to the south.

Fig. 2. Head of a male Japanese Pygmy Woodpecker (left) and his redfeather (right).

Vocalization:
Japanese Pygmy Woodpeckers utter "Ghee, giggi" or "Dzueei, Ki,ki-ki-ki-ki-ki-ki". They call "Ghee" in a soft voice when they identify each other in a pair or family. They give out "Kikki" in a sharp
tone when they assert themselves.

Distribution and Habitat
Distribution:
Japanese Pygmy Woodpeckers are distributed in most regions ofJapan from Hokkaido to Okinawa, and in the Korean Peninsula,eastern China and southern Sakhalin. In Japan, they also occur inmost small islands around the mainland including Iriomote Island,
one of the southernmost islands of Japan, where they are assumed
to be sparsely populated and therefore small in number. However,they are not found in Sado Island, Niigata Prefecture and OshimaIsland of the Izu Islands, which are relatively large and wooded aswell as close to the mainland. The species is classified into ninesubspecies in the Check List of Birds of Japan 7th ed.
(2012).
4♪ http://www.bird-research.jp/1_shiryo/koe/kogera_060706_mooka_mju.mp3
Mutsuyuki Ueta

Kogera (Jpn) Dendrocopos kizuki

Habitat:Japanese Pygmy Woodpeckers breed in a wide variety of woods,
ranging from an urban green space to a natural forest, such as abroad-leaved deciduous forest, a broad-leaved evergreen forest, asubarctic coniferous forest and a mixed forest of coniferous andbroad-leaved trees.

Life history
123

45

6

non breeding breeding period
period

7

8

9

10

1112

dispersal of young

Nest:
Japanese Pygmy Woodpeckers usually excavate a nest hole in the dead branch of alive tree. The hole is about 15cm deep withan entrance about 3cm across. They excavate a new hole every year. They use almost
no nest materials except that a few woodchips sometimes remain in a nest. Bothmales and females excavate a nest hole, butmales mostly carry out the task.

Fig. 3. Cavity of Japanese Pygmy
Woodpeckers.

Egg:The mean egg size is 18.9mm (18.0-20.3mm) by 14.5mm (12.515.3mm). The weight is about 2g and the color is white with noflecks.

Incubation and nestling periods:
They lay one egg a day in the early morning. The study conducted
mainly in Tokyo showed that the clutch size was mostly 3 eggs
(range: 2-5 eggs). They started to incubate when they laid the lastegg. The incubation and nestling periods were about 14 and 20days, respectively. Both males and females incubated eggs andnestlings, but males did more frequently.

Post-fledging:
Juveniles usually leave the territory of
their parent birds two or three months
after fledging, though they sometimes
remain until next March. The dispersal of juveniles is still unknown, butthere is a record of the young malewhich nested in a tree about 130m
from the nest tree he fledged the previous year in Shakujii Park, Tokyo(Fig. 4).

Fig. 4. An example of ayoung male dispersal(Shakujii Park in Tokyo).

Diet and foraging behavior
The diet of Japanese Pygmy Woodpeckers consists of the seeds ofplants, such as Rhus trichocarpa, R. javanica and Cornus controversa as well as arthropods, such as insects and spiders. They generally peck at invertebrates such as insects on tree trunks, branches
and leaves or under barks, or bore a small hole in trunks andbranches to capture them inside. They may capture small skinks
because they were observed to hold them in the bill.

Topics of ecology, behavior and conservation● Equal division of roles between males and females andstrong pair-bond
In most of the Japanese Pygmy Woodpecker pairs I measured,
females exceeded males in tarsus length, wing length, weight andother measurements. The red feathers on the head that characterizemales can be invisible in the field because they are short and small♪ http://www.bird-research.jp/1_shiryo/koe/kogera_080516_utsunomiya_hirano.mp3
Toshiaki Hirano

Bird Research News

Vol.2 No.5

2005. 5.11. Last Revised:2014.4.10.

© Japan Bird Research Association
Sumiyoshi 1-29-9, Fuchu, Tokyo, Japanin number. It may be related 45%
Femaleto their cooperative breeding
Malesystem by sharing similarroles that there is no great 30
difference in morphology
between the sexes and females which lay eggs are 15
larger than males. In short, it
is biologically reasonable 0
that females are larger be<14 <14.5 <15 <15.5 >15.5 mm
cause they produce ova
Fig. 5. Difference in tarsus length
which are larger than sperms
between the sexes (measured in themales produce. As a matter
breeding period)of fact, females are larger
than males in many of the sexually reproducing species. In thespecies where the physical strength of males decides a dispute forfemales, which increases their reproductive success, males arelarger than females, but it is not assumed to be an important attribute to Japanese Pygmy Woodpecker males.
The male and female of a pair stay together, except when theyroost, excavate a nest hole, and incubate eggs and nestlings. They
softly whisper "Ghee ghee" very frequently when they move together. This call makes it easy to detect them. They are assumed toconfirm each other by exchanging calls in this way. This call isalso used in a family flock with fledglings.
Two pairs of the same individuals were confirmed to breed forthree years consecutively in Tokyo (Taga 1988, Dobashi 1989).
An observation showed that when one bird called "Kik-kik-kik"sharply in the treetops at daybreak, another bird flew directly tojoin it and then both birds began to move together.
I once kept a few Japanese Pygmy Woodpeckers and Great Spotted Woodpeckers (Dendrocopos major) for several years for ascientific purpose. I kept Japanese Pygmy Woodpeckers in a cageat home to take care of them everyday in most of the study period.
Although the Japanese Pygmy Woodpeckers did not particularly
take to me, but they called "Kik-kik-kik" to me whenever I camehome unlike the Great Spotted Woodpeckers. As mentioned
above, Japanese Pygmy Woodpeckers have a habit of attempting
to maintain a close-knit pair relation. This habit probably madethem behave like that toward a human.

● Modest drumming and strong vocalization
All woodpeckers make a loud sound by beating the wood repeatedly with their bill, which is called "drumming", when they claim
their territory or summon their mate. In recent years, some woodpeckers have also used the metallic part of a utility pole for drumming. Though Japanese Pygmy Woodpeckers also do the drumming, the sound does not carry a long distance because they keep
the drumming modest (about 10 soft beatings per 0.4 seconds). But
they shrill "Kik-kik-kik-kik", which can be heard from a distance.
This call is assumed to perform a function, such as a territorial
claim instead of the drumming as in the high-pitched “Pyoo” noteof Japanese Green Woodpeckers (Picus awokera). Japanese Pygmy Woodpeckers utter this "Kik-kik" call when they make claims
strongly. Nestlings may make a sound similar to this call when
begging for food.

● Inexplicable absence of Japanese Pygmy Woodpeckers inOhshima of the Izu Islands and Sado Island
Though Japanese Pygmy Woodpeckers live in many islands of theJapanese Archipelago, they do not occur on Ohsima of the Izu
Islands and Sado Island. Both islands have large enough woodlands for Japanese Pygmy Woodpeckers. As a matter of fact, they
are commonly found in the mainland just 30km from the islands.

バードリサーチ生態図鑑
On Sado Island, however, White-backed Woodpeckers (D. leucotos) and Great Spotted Woodpeckers occur which are by far
larger than Japanese Pygmy Woodpeckers. In the Izu Islands, on
the other hand, Japanese Pygmy Woodpeckers live on Miyakejima
and Mikurajima Islands which are located at a greater distancefrom the mainland than Ohshima Island. Have they not settled
there? Or become extinct? It is mysterious and interesting why
they are absent from the islands.

● Pruning of dead tree branches suitable for JapanesePygmy Woodpecker nest hole in cities
In wooded parks and on school campuses branches with nest holesof Japanese Pygmy Woodpeckers have been also cut one after
another under the pretext of safe traffic or scenic preservation. It is
not uncommon for Japanese Pygmy Woodpeckers to lose theireggs or nestlings due to cutting of branches with their nest holes
after they have laid eggs. Once I found Japanese Pygmy Woodpecker nestlings drowned in a pond because the nest tree fell intothe water.
When I carried out a close check on dead branches in hills andmountains, I found that dead branches suitable for Japanese Pygmy Woodpecker nest holes were in shorter supply than expected,
which suggests that they need a large territory (about 20ha) for asmall bird to secure suitable dead branches for their nesting.

Literature
Dobashi N. 1989. Japanese Pygmy Woodpecker pairs that is individually identified
and bred in Itawabshi Ward, Tokyo. Strix 8:161-168. [J+E]
Ishida K. 1997. Great Encyclopedia of Japanese Animals Vol. 4 "Birds".
Heibonsha, Tokyo. [J]Ishida K. & Taga R. 1988. The flora of Musashino wildwood and the distribution ofnest holes of Japanese Pygmy Woodpeckers in Bajikoen Park, Tokyo. Strix
7:213-230. [J+E]
The Ornithological Society of Japan. 2012. Check-list of Japanese Birds (the 7thedition). [J+E]
Taga R. 1988. The nesting record of the Japanese Pygmy Woodpecker in Bajikoen
Park in Tokyo. Strix 7: 291-295. [J+E]
Yoshii T. (ed.). 1988. Concise Dictionary of Bird Names. Sanseido, Tokyo. [J]Japanese Pygmy Woodpecker Research Page of Ishida Laboratory in the Universityof Tokyo.
http://www.uf.a.u-tokyo.ac.jp/~ishiken/japanese/kogera/kogera.html
Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

AuthorKen ISHIDA the University of Tokyo
Though Japanese Pygmy Woodpeckers are my all-time favorite birdand I would like to be absorbed in their study, I am also engaged forvarious reasons in the ecosystem conservation and management ofAmami-Ohshima Island, and research on fruition properties of Quercus mongolica. I have captured and studied Asian black bears andstudying birds in the areas
around Fukushima Daiichi
Nuclear Power Plant after
the accident as well. WhenI retired, I will set out on a
study trip across Japan andeast Asia, capturing andmeasuring Japanese Pygmy
Woodpeckers and its relatives.
ishiken@es.a.u-tokyo.ac.jp

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