Bird Research News

Vol.9 No.2

Crested Serpent Eagle

2012.2.24.

Kanmuri-Washi (Jpn) Spilornis cheela

Morphology and classification
Classification: Accipitriformes Accipitridae
Total length:♂ 51.3cm (49.9-53.0cm)
Wing length:♂ 35.3cm (32.7-36.5)
Tail length:♂ 23.0cm (21.8-24.9)
Culmen length: ♂ 28.9mm (27.4-30.0)
Tarsus length: ♂ 79.4mm (75.0-82.5)
Weight:♂ 731g (670-780g)♀ 52.2cm (50.5-53.7)♀ 35.7cm (34.1-37.5)♀ 23.9cm (21.1-25.3)♀ 29.0mm (27.9-30.2)♀ 78.7mm (74.4-82.8)♀ 756g (700-840)

Perplexus is not a subspecies but another species S. perplexus(Ferguson-Lee & Christie 2001).

Habitat:
Adult birds prefer a habitat composed of woodlands, rivers andmangrove swamps. They generally use woodlands as a nest siteand swamps as a foraging ground. They also feed in open areas,such as rice paddies, meadows and cane fields. Young birds without established territories use small secondary forests, shrine andtemple woods, cropland, rice fields and coastal forests.

Measurements of rescued adults in Ishigakijima Island by Sano (excluding individuals
intensely weakened or damaged). Based on 7 males and 5 females.

Life history

Appearance:

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Adult Crested Serpent Eagles arebrownish black on the upperpart andbrown or grayish brown with numerous white speckles on the underpart. They are black on the crownwith a crest on the back of the head,
which gave rise to the Japanese andEnglish names. The crest is barely
noticeable, however, except when
they become tense and raise it. The
iris is generally yellow, but somebirds have dark brown irises regardless of sex or age. The feet and bareskin around the eye are yellow. The
beak is bluish gray. They have two
broad black bands on the flight and
tail feathers. Juveniles are white on
the upperpart with dark brown or
black stripes, which makes the backlook scattered with black and whitespecks from a distance. The underpart is conspicuously white. There
are a wide range of individual variations in a black patch behind theeye. This patch is absent from somejuveniles, while it has an intricate
pattern in others. The iris is pale Photo 1. Adult (above) andjuvenile (below) of Crestblue or yellowish green. Juveniles
ed Serpent Eagles .
also have black bands on the flightand tail feathers, but they are narrower and more numerous than inadult birds.

Vocalization:
The resonant territorial call which sounds like "Kuk-kuk-kuk, fi-fifi-feefee" is typical of Crested Serpent Eagle vocalization. They
relatively often utter this call from late January to May. They givea single shrill cry going like "Fee" as a alarm call. They also call"Bee, bee" or "Hee, hee"in a husky voice. Females call "Kew-ooi,kew-ooi" in a wheedling voice before copulation or when receiving food from males (Sano 2003b). More than six kinds of vocalizations are confirmed including "Whoeeeyo, whoeeeyo" whichmales utter to call females before food transfer and nestling calls.

Distribution and Habitat
Distribution:
Crested Serpent Eagles are widely distributed in South and Southeast Asias, such as India, Sri Lanka, southern China, Taiwan, theMalay Peninsula, Sumatra, Java, Kalimantan, Sulawesi and thePhilippines (Dickinson et al. 2003). A Japanese endemic subspecies S. c. perplexus of Crested Serpent Eagles occurs as a yearround resident and breeds in Ishigaki and Iriomote Islands, Okinawa Prefecture (the southernmost prefecture of Japan). Some authors have recently proposed a theory that this S. c.

4♪ http://www.bird-research.jp/1_shiryo/koe/kanmuriwashi_050409_okinawa_kaji.mp3
Kyoko Kajimoto

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copulation &nest building incubation nestling

89

10family periodwith fledgling

11 12
fledging dateunknown

Breeding system:
Crested Serpent Eagles are a monogamous breeder. They start tobuild a nest in late January and continue to carry the branchesintermittently until early April when they begin to lay eggs. Meanwhile, they copulate many times. Females mostly incubate eggs
and nestlings, while males provide food for females and nestlings.
Females also leave the nest in late June to forage for food. Nestlings fledge from mid-July to August. However, it is still unknown
when fledglings become independent.

Nest:
They build a nest on the slope of a moist valley covered with Luchu pines (Pinus luchuensis) and evergreen broad-leaved trees.
They generally use as a nest tree oaks Castanopsis sieboldii, Luchu pines and Indian laurels (Ficus retusa). They build a plateshaped nest at the fork of radial branches or on a lateral branchwith a tangle of vines using Luchu pines, Indian laurels and Fraxinus griffithi as a nest material. The nest size is reported to be 66cm
by 51cm in Luchu pine woods (Miyazaki 1981, Harato 1987, Sano2003a).

Egg:
The clutch size is 1-2 eggs in theliterature, but one newly hatchednestling was observed every year in
the nest where a pair of Crested
Serpent Eagles bred for three consecutive years, which suggests thatthe clutch size is usually one egg.
The egg is about the size of a Photo 2. A nestling.
chicken egg. The egg has reddish
brown speckles on an off-white ground (Miyazaki 1981, Harato
1987, Sano 2003a).

Incubation and nestling periods and fledging rate:
The incubation period is estimated to be 30-45 days. Nestlings
begin to move around the branches in the vicinity of the nest 60-70
days after hatching (Yoshimi 1991, Sano 2003a).

Diet and foraging behavior
The diet of Crested Serpent Eagles consists of various animals,
such as amphibians, reptiles, small mammals, birds, fish, crustaceans, insects, chilopods, thelyphonida and earthworms. Theyoften prey on vipers Trimeresurus elegans and introduced marine
toads (Bufo marinus) that secrete venom from parotoid glands.
They also capture Asian house shrews (Suncus murinus) with astrong smell and Typopeltis crucifer. Sano (2003a) reported that thediet of nestlings included frogs (27%), crabs (13%), skinks (11%)
and snakes (6%). They primarily still-hunt, namely they perch on atree and an utility pole to wait for the prey and swoop down on it
when they detect it beneath. Experienced birds also use humans toVol.8 No.2

2012.2.24.

© Japan Bird Research Association
Sumiyoshi 1-29-9, Fuchu, Tokyo, Japan● Sighting records of Crested Serpent Eagles outside
Ishigaki and Iriomote Islands
Crested Serpent Eagles occur as a year-round resident and breed inIshigaki and Iriomote Islands, but they have been sighted in theneighboring islands as well. There were two sighting records offTarama Island in the 1980s (Hisagai & Yamamoto 1981, Hisagai1998) and three in Yonaguni Island in the late 1970s to the early
1980s (Koyama et al. 1980, the Agency of the Environment 1982).
Since Yonaguni Island is close to Taiwan (ca. 110km), however, theobserved birds may have belonged to the subspecies of Taiwan. In
addition to these older records, one juvenile was observed in thecoastal forest of Taketomi Island in the winter of 2004-2005(Kikuchi & Sano 2007) and seven birds were sighted in the vicinityof the coastal forest of Obama Island between 1995 and 2007
(Takahara 2004, the Ministry of the Environment 2008). A subadultbird with some juvenile plumage was rescued in Obama Island in2010. The bird was banded and released later to be found in Iriomote Island in 2011 (the Iriomote Wildlife Conservation Center ofthe Ministry of the Environment per. comm.). Since no ages were
described in the sighting records before 2000, it is unknown whether
the sighted birds were adults or juveniles, but young birds have beenrecorded in recent years, which suggests that they temporarily use
islands around Ishigaki and Iriomote Islands, which are not available to them due to severe territorial rivalry with adult birds. It is
important to accumulate these records to understand the movementand dispersal of Japanese Crested Serpent Eagle population andconserve the habitats.

● Increasing traffic accidents of Crested Serpent Eagles
In Ishigaki and Iriomote
Islands, 9.5 and 5.3 moribund or dead Crested Serpent Eagles on average arerescued or collected everyyear, respectively. Traffic
accidents represent 54% of
the contributory factors(based on the 2000-2001
study of the Crested Serpent Eagle Research).
Along with the construction

Photo 3. A Crested Serpent Eagle feeding
on a road. Since the eagles tend to
take flight at the last moment when a
car approaches, it is at risk from aroad accident.

11年

10年

09年

08年

07年

06年

05年

04年

Since Crested Serpent Eagles nest in a dense forest with low visibility, it is difficult to observe them in the nest site, which is responsible for the lack of nesting records and observations. When they areperched on a utility pole and a tree at the edge of a forest, on theother hand, it is easier to observe them than other birds of prey because they are more tolerant of humans. It is possible, therefore, toconfirm detailed plumage coloration, sexes, ages and leg bands.
Even unbanded birds may be identified based on facial features inparticular, which can help determine the home range of establishedadult birds. There have recently increased the tourists who takephotographs of Crested Serpent Eagles perched on a utility pole by
the roadside in Ishigaki and Iriomote Islands and upload them intheir blogs. Some of these images include valuable information on
leg bands or facial features. The Crested Serpent Eagle Research（http://kanmuriwasi.web.fc2.com/) collects information on banded
birds and juvenile facial photographs every year to attempt to determine the population of Crested Serpent Eagles.

03年● Easy to observe due to a relatively high tolerance for humans

02年

Topics of ecology, behavior and conservationof roads and traffic increase, recent years have found more small
animals that are killed in a traffic accident or fall into a ditch at theside of a road. Crested Serpent Eagles that scavenge for these roadkills have been involved in a14
traffic accident as well (Photo.
石垣西表■ Ishigakijima
Island■ Iriomotejima Island3; Fig. 1). The Crested Serpent 12Eagle Research has called for 10
drivers to be cautious of Crest- 8
ed Serpent Eagles by distrib- 6
uting handouts, while we are 4
engaged in the rehabilitation 2
and release of Crested Serpent 0
Eagles injured in a traffic accident with the cooperation of the Fig. 1. Number of traffic accidents
local administration and veteriinvolving Crested Serpent Eanary hospitals as well as colgles since 2000 (By the Crested
lecting information on birds
Serpent Eagle Research).
released back into the wild.
00年

secure food. For instance they capture small animals driven out ofcover by grass harvesting and levee burning or trapped in a ditch at
the side of a road. They may also scavenge road kills.

バードリサーチ生態図鑑

01年

Bird Research News

Literature
Dickinson E.C. (ed.) 2003. The Howard & Moore Complete Checklist of the Birdsof the World. 3rd Edition. Princeton University Press, Princeton, New Jersey.
Ferguson-Lees J. & Christie D.A. 2001. Raptors of the World. Houghton Mifflin,Boston.
Harato T. 1987. Food habits and behavior of a fledgling of the Crested
Serprent-eagle，Spilornis cheela perplexus，iniriomote-jima island，okinawa.
Island studies in Okinawa (5): 49-58. [J+E]
The Ministry of the Environment Naha Natural, Environmental Office. 2008.
Report on the private specific use of the National Park nature environmental
preservation activity business (research on the Crested Serpent Eagle state). pp.
56-60. [J]Environment Agency. 1982. The current state of the Crested Serpent Eagle in theYaeyama Islands. Special bird survey in 1981 fiscal year S.56. pp. 53-75. Environment Agency, Tokyo. [J]Kikuchi S. & Sano K. 2007. A record of the Crested Serpent Eagle on Taketomijima Island of the Ryukyu Islands southwestern Japan. Bird Research 3: S7-S10.
[J+E]
Koyama K., Koga M., Fujikado K., Dejima K. & Uyama T. 1980. Wild bird in
Okinawa in winter. Yacho. 45(5): 40-43. [J]Kugai K. & Yamamoto A. 1981. Bird list of the Miyako Islands. Okinawa Biology
Education Society Journal 14: 15-29. [J]Kugai K. 1998. Birds in Taramajima & Minnajima Islands. Bulletin of Hira CityMuseum 5: 39-68. [J]Miyazaki M. 1981. Eagles and hawks. Heibonsha, Tokyo. [J]Sano K. 2003a. Breeding biology of the Ryukyu Crested Serpent Eagle in Ishigaki
Island, Okinawa. Strix 21: 141-150. [J+E]
Sano K. 2003b. The present state of the Series "Let's protect this bird." "Ayapani(Crested Serpent Eagle)" -The eagles respected and sung in traditional songs-.
Our Nature 44(4): 16-19. [J]Sano K. 2010. Photographs of juvenile Crested Serpent Eagle face are recruited.
Bird Research News 7(12): 5. [J]Kasahara K. 2004. On the record of birds on Obama Island. Obama Island generalsurvey report. Pp. 35-59. Okinawa Prefectural Museum, Naha City. [J]Yoshimi K. 1991. The Crested Serpent Eagle in Iriomotejima Island. JapaneseAnimals 5(3): 4-15. [J]AuthorKiyotaka SANO Crested Serpent Eagle Research
Crested Serpent Eagles are a well-known birdin name only partly because they are designated as a special natural monument. In Ishigakijima Island they are used for the names of aCoast Guard helicopter and a project for improving scholastic ability as well as the mascot of New Ishigaki Airport which will beopened soon. However, these eagles havecreated images divorced from the actual ecology and the current critical state of the species. It is 15 years since I
started to study Crested Serpent Eagles and six years since this working group was established. I intend to supply more information on
Crested Serpent Eagles as they really are in the future.

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