Reintroduction  (2012)  2: 43 – 50

Ezaki and Ohsako: Stork breeding biology

ORIGINAL ARTICLE

Breeding biology of the Oriental White Stork reintroduced inCentral Japan—Effects of artificial feeding and nest-tower arrangement upon breeding
season and nesting success—* Yasuo Ezaki1,2 and Yoshito Ohsako2
Abstract Reintroduction of the Oriental White Stork
Ciconia boyciana into Tajima District, Hyogo Prefecture

Introduction

started in 2005 and the population size is increasing with

A wild population of the Oriental White Stork Ciconia

successful breeding in the wild. Our study on the reintro-

boyciana existed in Tajima District, northern part of

duced population composed of banded birds evidenced

Hyogo Prefecture until ₁₉₆₀＇s, but it was extinct in ₁₉₇₁.

that the pair once formed continues to breed in a same

Just before extinction the small number of storks that sur-place and the pair-bond continues over years. Eight pairs

vived in the wild was captured, and an attempt of captive

laid 29 clutches including 3 replacement ones in 5 years

breeding started in aviaries constructed in Toyo-oka City.

between 2007 and 2011. From information on the day of

The success was brought about in ₁₉₈₉ by a pair of storks

egg-laying, hatching, ﬂedging of these clutches, it wastransferred by Russian Government. Thereafter captive

concluded that incubation and nestling periods are 31–35

population size increased over ₁₀₀, and reintroduction

days and 63–74 days, respectively. Thus it takes about 100

started in ₂₀₀₅. Seven birds being the van for the year, ₂₇

days from egg-laying to ﬂedging of young. Egg-laying

birds in total were released into the wild by Hyogo Park

started between early March and late April and ﬂedging

of the Oriental White Stork (HPOWS), a prefectural insti-

occurred from mid-June to late July excluding those bytute specializing in reintroduction of the stork that waspairs that were fed enough artiﬁcially. They laid eggs andestablished in ₁₉₉₉ and taking over the aviaries. It was inﬂedged young exceptionally early. Clutch-size was 3 or 4

₂₀₀₆ that the ﬁrst clutch was laid in the wild, and in ₂₀₀₇

in most cases, whereas clutch-size of 6 was available only

the ﬁrst chick ﬂedged after ₄₆ years from the last ﬂedging

from artiﬁcially well-fed pairs. Success rate of the ﬁrst

in the wild in Japan and population size is increasing

clutch of a year to ﬂedge at least one young was 0.65 andthereafter (HPOWS, ₂₀₁₁).

the probability of an egg to ﬂedge was 0.34. The average

Pairs of the Oriental White Stork have territories

number of ﬂedglings was 1.2 birds per ﬁrst clutch of thethroughout a year (HPOWS, ₂₀₁₁) and after reintroduc-

year. Chicks were killed by predators and neighbouring

tion most of the pairs bred on artiﬁcial nest-towers built

territory owners, and parental infanticide occurred in

by various kinds of stakeholders including the Govern-

three nests. The effects of artiﬁcial feeding and nest-tower

ment of Hyogo Prefecture, the Government of Toyo-oka

arrangement on breeding are discussed.

City, HPOWS and residents of the City. Some of the tow-

Key words Breeding season, Ciconia boyciana, Clutch

ers are built in the open space in paddy ﬁeld area, differ-size, Infanticide, Pair-bond, Reintroduction

ent from the past wild population that nested on top oflarge pine trees on the hill-side facing paddy ﬁeld (Iwasa,
₁₉₃₆a,b). And some of the pairs have raised their young

₁

Division of Ecology, INES, University of Hyogo/Museum of
Nature and Human Activities, Hyogo, Yayoi-ga-oka ₆, Sanda,
Hyogo ₆₆₉-₁₅₄₆, Japan
₂
Division of Rural Ecology, INES, University of Hyogo/Divisionof Research, Hyogo Park of the Oriental White Stork, Sho-unji
₁₂₈, Toyo-oka, Hyogo ₆₆₈-₀₈₁₄, Japan* E-mail:depending on ﬁsh artiﬁcially supplied.
In this paper we report breeding biology of the Oriental
White Stork reintroduced in Hyogo Prefecture, Japan
based on data acquired for pairs that bred between ₂₀₀₇
and ₂₀₁₁, and discuss effects of artiﬁcial feeding and nesttower arrangement. Scientiﬁc information on ecology and43

Reintroduction（2012）2: 43 – 50

breeding biology of the past Japanese wild population isrestricted to Yamashina (₁₉₄₁). Information on wild populations that breed in Russia and China, on the other hand,
is mostly descriptive. Thus this paper probably is the ﬁrst
one that reports on breeding biology of this species withenough quantitative data.

Study area and methods
Toyo-oka City where the reintroduction project has
been carried out is situated at the northernmost part of
Hyogo Prefecture facing Japan Sea. River Maruyama
flowing from south to north forms a large floodplain
called Toyo-oka Basin surrounded by low-elevation hills,
suitable for breeding of the Oriental White Stork in thewild.
Released birds are all colour-banded and are identiﬁable individually. Pairs nested in ₉ rural areas of Toyo-oka
City, namely Akaishi (initialed as A), Fukuda (F), Hinado(H), Izu (I), Nojo (N), Sho-unji (S), Toshima (T), Yuruji(Y) and Yamamoto (YM). Fig.₁ shows distribution of thenest towers used by pairs with information on the locationof HPOWS. It can be seen that some nest-towers are set
back and located more than ₁km from the main ﬂow ofRiver Maruyama like F, N, H, S and YM, whereas T, A,

Fig. ₁. Study area and distribution of nest-towers used by pairsof the Oriental White Stork. Hills higher than ₂₀ m above sea
level are shaded. Nest name is same with the area name, Akaishi(A), Fukuda (F), Hinado (H), Izu (I), Nojo (N), Sho-unji (S),Toshima (T), Yuruji (Y) and Yamamoto (YM). The nest-tower of
H was not used and the pair nested on a telegraph pole nearby. A
sign of star indicates the location of the main premise of HPOWS
in Sho-unji area.

Y and I are located near that or near River Izushi thatjoins the main ﬂow at the ₁₅ km spot upstream from theof captive storks within the two distinct premises ofriver-mouth. Moreover Y is almost at the centre of an

HPOWS, situated in Sho-unji (the main premise) andextensive open space of paddy ﬁeld. Many of the pair

Nojo (the branch aviaries), respectively. The nesting on

members often ﬂy to an open cage of HPOWS during thethe pole and the cage has been artiﬁcially disturbed in

non-breeding season and forage that, where ﬁsh are sup-order to avoid electric accidents and intra-speciﬁc infec-

plied to storks displayed for public all the year round thattion of diseases from the wild to captive birds. Despite

are kept flightless by regular feather-cutting. Pair Y

these disturbances some pairs laid clutches on nests put(meaning the pair that nested in area Y) that ﬂedged theon the pole or on the cage. The examples are the clutchﬁrst chick in ₂₀₀₇ had been fed enough (₁ kg of ﬁsh/day)laid by pair N in ₂₀₀₈ that nested on a cage located in theby HPOWS all the year round in order to solicit theirbranch aviaries of Nojo, pair N in ₂₀₀₉ that nested on asettlement in the ﬁrst stage of reintroduction until it was

telegraph pole, pair S in ₂₀₀₉ that nested on a cage in thecompletely stopped in ₂₀₁₂. Pair T has been regularly fed

main premise of HPOWS in Sho-unji and pair H in ₂₀₁₀

about ₅₀₀ g of fish by a NPO managing the wetlandthat nested on a telegraph pole. Of them, pair S in ₂₀₀₉

including the nest-tower during winter and the breedinggave up breeding but from other ₃ clutches chicks ﬂedged

season until it was completely stopped in ₂₀₁₂. Pair N has

as shown in results. In this paper we name each pair bybeen fed a little, irregularly and privately. Other pairs

combining the year and area name (e.g. ₂₀₁₀S) and often

were not fed artiﬁcially within their territories. Other thanby area name only.

on nest-towers, storks often tried to nest on telegraph

Nest towers are ₈.₀－₁₂.₅ m high and it is not easy topoles that exist all over Toyo-oka Basin and on the cages

conﬁrm the nest content until chicks grow up and become44Ezaki and Ohsako: Stork breeding biology

visible from the ground. But we made every effort to con-

was the only non-banded adult female with no young

ﬁrm the nest content throughout the nesting period byfeathers during the study period, probably a wild immi-

watching directly using ₈x binoculars and ₂₅x telescopes

grant from the continent. Nesting places of a same pairfrom higher places on the hill, sometimes from the top of

were also the same in principle. The only exception wasa mobile elevation system, and indirectly by using video

the pair between J₀₃₈₉ and J₀₃₈₄ that started on the nest-

cameras. In these cases we could determine the exact date

tower of A in ₂₀₀₇ but changed to the nest-tower of F inof ﬁrst egg-laying and ﬁrst hatching in a nest, and exact

₂₀₀₈ and returned to A in ₂₀₀₉. The youngest pair was

number of eggs and hatchlings. On the other hand, it was

₂₀₀₇A, both the male and the female being born ₃ years

very easy to watch and conﬁrm ﬂedging of young birds

before the ﬁrst breeding. And the male of ₂₀₀₈N was ₂

directly.

years old when he joined the ﬁrst breeding. It should be
added that the age of a non-banded male of pair ₂₀₁₁YM
is estimated to be ₃, because non-banded ﬂedglings at that

Results

time were restricted to those from pair I in ₂₀₀₈.

Pairs and their nesting
Number of pairs that laid eggs in Toyo-oka Basin was

Breeding season and the length of nesting period

₂ in ₂₀₀₇, ₅ in ₂₀₀₈, ₆ in ₂₀₀₉, ₇ in ₂₀₁₀ and ₆ in ₂₀₁₁,

During the ₅ years ₂₆ pairs in total laid ₂₉ clutches

totaling up to ₂₆ in ₅ years (Table ₁). It can be seen that

including ₃ replacement ones after failure (Table ₂). Of

the pairs bred continuously every year with the same matethe ₂₆ ﬁrst clutches no eggs hatched from ₆ clutches (codeonce they started breeding, except the cases where the₂, ₉, ₁₃, ₂₁, ₂₅ ₂₆), resulting in ₇₇％ (₂₀/₂₆) of hatchingmales were dead in accidents at the start of the breeding

success per clutch. The exact day of ﬁrst egg-laying of theseason. Although the female of pair S between ₂₀₀₉ andyear is known for ₉ pairs (code ₁₀, ₁₂, ₁₃, ₁₆, ₁₇, ₁₉, ₂₀,₂₀₁₁ was not banded, it is highly possible that it was the₂₃, ₂₅) and with a few days of estimation ranges for ₄

same individual throughout the study period, because she

clutches (code ₁, ₆, ₁₈, ₂₆). Of these ₁₃ clutches, the ear-

Table ₁. Nest site of storks that bred between ₂₀₀₇ and ₂₀₁₁ and their age of ﬁrst
breeding. Males and females occupying a same nesting site in a year is a pair.
Banded birds have their own individual codes and NB indicate non-banded birds.
Regarding the age of a non-banded male, refer to the text.
Individual
code

Sex

J₀₂₇₅
J₀₂₂₈
J₀₃₈₉
J₀₃₈₄
J₀₃₉₁
J₀₂₉₄
J₀₀₀₁
J₀₃₆₂
J₀₃₈₁
J₀₂₉₆
J₀₄₀₅
NB
J₀₄₀₈
J₀₀₀₂
NB
J₀₃₉₉

male
femalemale
femalemale
femalemale
femalemale
femalemale
femalemale
femalemale
femaleYear of
Birth
₂₀₀₀
₁₉₉₈
₂₀₀₄
₂₀₀₄
₂₀₀₄
₂₀₀₁
₂₀₀₆
₂₀₀₃
₂₀₀₄
₂₀₀₁
₂₀₀₆

unknown
₂₀₀₆
₂₀₀₆
₂₀₀₈
₂₀₀₅

Nest site
₂₀₀₇

₂₀₀₈

₂₀₀₉

₂₀₁₀

₂₀₁₁

Y
Y
A
A

Y
Y
F
F
T
T
N
N
I
I

Y
Y
A
A
T
T
N
N
I
I
S
S

Y
Y
A
A
T
T
N
N
I
I
S
S
H
H

Y
Y
†

Age of ₁st
breeding
₇
₉
₃
₃
₄
₇
₂
₅
₅
₇
₃

T
T
N
N
I
I
S
S

unknown

YM
YM

₄
₄
₃
₆

†

Y: Yuruji; A: Akaishi; F: Fukuda; T: Toshima; N: Nojo; I: Izu; S: Sho-unji; H: Hinado;
YM: Yamamoto†: dead in accidents at the start of the breeding season

45

Reintroduction（2012）2: 43 – 50

Table ₂. Breeding season of the Oriental White Stork and length of incubation, nestling and nesting periods,
the last meaning those from the day of ﬁrst egg-laying to ﬂedging of the ﬁrst chick, for the ﬁrst clutch of theyear by each pair (a) and for replacement clutches after failure (b). The day of each event is not always exactly
known and a sign ＂～＂ is used when the event occurred on or before the day. Code number is given for eachof the ₂₉ clutches. Pairs with asterisks nested on the telegraph pole or on the cage of captive storks.
a)Code no. Pair name
₁
₂
₃
₄
₅
₆
₇
₈
₉
₁₀
₁₁
₁₂
₁₃
₁₄
₁₅
₁₆
₁₇
₁₈
₁₉
₂₀
₂₁
₂₂
₂₃
₂₄
₂₅
₂₆

₂₀₀₇Y
₂₀₀₇A
₂₀₀₈Y
₂₀₀₈F
₂₀₀₈T
₂₀₀₈N*
₂₀₀₈I
₂₀₀₉Y
₂₀₀₉A
₂₀₀₉T
₂₀₀₉N*
₂₀₀₉I
₂₀₀₉S*
₂₀₁₀Y
₂₀₁₀A
₂₀₁₀T
₂₀₁₀N
₂₀₁₀I
₂₀₁₀S
₂₀₁₀H*
₂₀₁₁Y
₂₀₁₁T
₂₀₁₁N
₂₀₁₁I
₂₀₁₁S
₂₀₁₁YM

Code no.

Clutch
name

₂₇
₂₈
₂₉

₂₀₁₀Y
₂₀₁₁Y
₂₀₁₁S

Start ofDays ofegg-laying

hatching

ﬂedging

incubation

nestling

nesting

₁₄-₁₈ April～₁₀ April～₄ March～₂₆ March

₁₉-₂₀ May

₃₁ July

₃₁-₃₆

₇₂-₇₃

₁₀₃-₁₀₉～₂₂ March～₂₀ April
₂₈ April
₁ May～₁₄ May
₁₁ March

₄ June₂₂ June₂ July₃ July₂₀ July
₂₄ May

≧₉₂
≧₈₈

≧₂₇

≧₇₄
≧₆₃
₆₅
₆₃
≧₆₇
₇₄

₉₄-₉₇
≧₁₁₁
≧₁₀₁

₂ April
₂₂ April
₁₁ May₉ June₂₉ June₁₆ July

₃₄
≧₃₁
₃₃

₆₈
₆₈
₆₆

₁₀₂
≧₉₉
₉₉

≧₆₄
≧₇₂

₁₀₈

₆₇
₇₂

₉₈
₁₀₆

≧₆₄
₆₅
₆₆

≧₉₉
₉₈

₂₈-₃₁ March～₃₁ March～₁₂ February～₂₁ April
₂₈ February～₂₂ March
₈ April
₁₆ March～₂₃ February
₂₁ February
₂₁ April
₂₂-₂₃ March
₁₇ March
₁₆ March～₂₁ April～₂ March
₂₆ March～₂₇ March～₁₁ April～₂₈ March
₂₆ May～₂₈ April
₁₇ April
₁₉ April～₆ April
₂₈ April～₁₂ May

₁₄ June₈ June₂₃ June₃₀ June₉ June₂ July₁₇ July

₃₁-₃₄

≦₃₆
₃₅
≦₃₆
₃₁
₃₄

₃₃

₉ March₁₆-₁₇ Marchb)
Start ofDays ofegg-laying

hatching

ﬂedging～₁ June～₂₉ June
₁₄ April～₃₀ June～₁₈ July
₁₇ May₂₉ August
₂₁ September
₂₀ July

incubation

nestling

nesting

₃₃

≧₅₃
≧₆₅
₆₄

≧₈₉
≧₈₄
₉₇

liest egg-laying occurred in February for ₂₀₀₉T (code ₁₀

for all of the ₁₇ ﬁrst clutches that were successful. Hereon ₂₈ Feb.) and ₂₀₁₀T (code ₁₆ on ₂₁ Feb.) that were fed

also, the earliest records are available in regularly fed

regularly. And pair Y that were fed enough is known topairs (code ₃ and ₈ in May or early June by pair Y, code

have started egg-laying in February of ₂₀₀₉ and ₂₀₁₀

₁₀ and ₁₆ in early June both by pair T). Excluding them,(code ₈, ₁₄), the former being the earliest of all clutches,

ﬂedging occurred from mid-June to late July (₁₄ June toalthough the exact day is not known (on or before ₁₂

₃₁ July). In ₃ replacement clutches egg-laying started inFeb.). Excluding the two regularly fed pairs, egg-laying

April or June and chicks ﬂedged from July to September.

started between early March and late April (₉ March-₂₁

Incubation period (days between ﬁrst egg-laying andApril). The date of ﬂedging of the earliest chick is known

ﬁrst chick hatching) is exactly known for ₆ ﬁrst clutches46

Ezaki and Ohsako: Stork breeding biology(code ₁₀, ₁₂, ₁₇, ₁₉, ₂₀, ₂₃), which is distributed in a range

ﬁrst clutches that completed clutches, breeding failed dur-of ₃₁–₃₅ days. For other ₂ clutches incubation periods

ing incubation period in ₅ nests (code ₂, ₉, ₂₁, ₂₅, ₂₆).

with estimation ranges, being ₃₁–₃₆ days (code ₁) andMortality factor of these eggs is not known. Brood-size,

₃₁–₃₄ days (code ₆), consist with the result from exact

the full number of hatchlings is exactly known for ₁₅

data. Information on other ₄ clutches (code ₈, ₁₁, ₁₆, ₁₈)

broods including the ₅ clutches that failed during incuba-

does not contradict the conclusion of ₃₁–₃₅ days of incu-tion (brood-size: zero). The average brood-size is calcu-

bation period. For nestling period, exact information is in

lated as ₁.₇ (₂₆/₁₅). If we exclude the ₅ clutches thata range of ₆₃–₇₄ days (code ₆ the shortest, ₈ the longest)

failed during incubation, the average brood-size is calcu-

and this range can explain all other ﬁrst clutches. The

lated as ₂.₆ (₂₆/₁₀).

nesting period, from ﬁrst egg-laying to ﬁrst young ﬂedg-

Chicks that ﬂedged from ₂₆ ﬁrst clutches total up to ₃₀

ing, is in a range of ₉₈–₁₀₈ days for ₆ clutches with exact

birds. Thus, the average breeding success is calculated asdata (code ₁₀, ₁₂, ₁₆, ₁₉, ₂₀, ₂₃). This range can explain

₁.₂ birds per ﬁrst clutch (₃₀/₂₆). Replacement clutches

all other clutches whose nesting period is not known

added ₇ ﬂedglings from ₃ nests. The interval between

exactly except code ₇ whose nesting period is ₁₁₁ days.

ﬂedging of different chicks in a nest is in a range of ₀

We can conclude that about ₁₀₀ days are required from(same day)-₆ days between ₁st and ₂nd ﬂedging, and ₀–₃

egg-laying to ﬂedging. Conclusions on incubation, nest-days between ₂nd and ₃rd ﬂedging (there was an excep-

ling and nesting periods as being ₃₁–₃₅, ₆₃–₇₄ and about

tional case of ₂₂ days between ₂nd and ₃rd in clutch-code

₁₀₀ days are consistent with the ₃ replacement clutches.

₁₂, whose ₃rd chick was not well nourished) including

replacement clutches (see Table ₃).
Clutch size and breeding success

Mortality factors during the nestling period are preda-

Seventeen of the ₂₆ ﬁrst clutches produced at least one

tion (one chick), parental infanticide (₄ chicks) and intra-

ﬂedgling, success rate per clutch being ₀.₆₅ (₁₇/₂₆). Nine

speciﬁc attack against nestlings (₁ chick). The predation

unsuccessful clutches include ₃ (code ₂, ₁₃, ₂₆) by pairs

occurred in the nest of pair I (code ₇) on ₂₀ May ₂₀₀₈. A

that bred for the ﬁrst time whose success rate is ₀.₆₃

Black Kite Milvus migrans attacked the nest while the(₅/₈), not different from ₀.₆₇ (₁₂/₁₈) by other pairs. The

parents were absent and carried away one of the ₃ nest-

female of pair S when she bred ﬁrst with the mate in ₂₀₀₉lings. The age of the chick is estimated to be about a few(code ₁₃) laid ₁₀ eggs, because the male of ₃ years olddays, if we count backward from the day of ﬂedging

mishandled and destructed eggs by himself three times

assuming nestling period as being ₇₀ days (see Table ₂).

(₁st to ₃rd eggs) and crows depredated the other eggs on

Parental infanticide was recorded in ₃ nests. On ₃₀ April

the day each egg was laid. This pair did not lay replace-₂₀₁₀ the female of pair S (code ₁₉) took a nestling thatment clutch this year (Table ₃). Video cameras were usedhatched about ₂ weeks before (see Table ₂) and deserted

to observe this clutch and the interval between each egg-

it outside the nest. The other ₂ nests are both by pair Y inlaying is known as ₂ days in three cases, ₃ days in ﬁve

replacement clutches (code ₂₇, ₂₈). On ₅ July ₂₀₁₀ thecases and ₄ days in one case. The interval of egg-laying

male of pair Y tried to swallow ₂ chicks that were theis precisely known for clutch-code ₁₉ by pair ₂₀₁₀S for

smallest of the ₅ nestlings (about two weeks after hatch-which video cameras were used again. The female in thising if we assume nestling period as being ₇₀ days, see

year laid ₄ eggs and the interval between eggs were ₂ days

Table ₂) but in failure, one of which being found deadin every case.

thereafter. And ₃ days later on ₈ July, the male took the

For ₂₅ clutches other than code ₁₃ by pair ₂₀₀₉S, ＂con-smallest of the surviving ₄ chicks and deserted it outside

cept of clutch-size＂ is applicable and the exact clutch-

the nest. On ₂₈ July ₂₀₁₁ the same male took the smallest

sizes are known for ₁₅ ﬁrst clutches, which is distributedof the surviving ₃ chicks from the nest of ₂₀₁₁Y andin a range ₂–₆ and the average clutch-size is ₃.₉ (₅₉/₁₅).

deserted that into a small pool on the ground near the nest

The largest clutch-size of ₆ was recorded for clutch-codesite. The age of the chick is estimated to be about two

₈ and ₁₄ both by pair Y that was artiﬁcially fed enough.

weeks if we assume nestling period as being ₇₀ days (seeOther pairs are not known to have laid ₆ eggs. Of the ₂₅

Table ₂). Intra-speciﬁc attacks were observed at ₂₀₀₉T



47

Reintroduction（2012）2: 43 – 50

Table ₃. Breeding success of the Oriental White Stork for the first clutch of the yearof each pair (a) and for
replacement clutches after failure (b). Number of eggs and nestlings are not always exactly known and signs ofinequality are used in such cases indicating the minimum number. Mortality factors during egg stage are notknown except for clutch-code ₁₃, the details being described in the text.
a)Code no. Pair name
₁
₂
₃
₄
₅
₆
₇
₈
₉
₁₀
₁₁
₁₂
₁₃
₁₄
₁₅
₁₆
₁₇
₁₈
₁₉
₂₀
₂₁
₂₂
₂₃
₂₄
₂₅
₂₆

₂₀₀₇Y
₂₀₀₇A
₂₀₀₈Y
₂₀₀₈F
₂₀₀₈T
₂₀₀₈N
₂₀₀₈I
₂₀₀₉Y
₂₀₀₉A
₂₀₀₉T
₂₀₀₉N
₂₀₀₉I
₂₀₀₉S
₂₀₁₀Y
₂₀₁₀A
₂₀₁₀T
₂₀₁₀N
₂₀₁₀I
₂₀₁₀S
₂₀₁₀H
₂₀₁₁Y
₂₀₁₁T
₂₀₁₁N
₂₀₁₁I
₂₀₁₁S
₂₀₁₁YM

Number of

Fledging interval (days)

eggs

nestlings

ﬂedglings

≧₃
₃
≧₅
₃
≧₃
≧₄
₃
₆
₄
₄
₄
₄
₁₀
₆
≧₁
₄
≧₄
≧₂
₄
₄
₂
₄
₄
≧₃
≧₄
≧₂

≧₂
₀
≧₃
≧₁
≧₃
≧₁
≧₂
≧₄
₀
₄
₃
₃
－
₂
≧₁
≧₂
₁
₁
₃
₂
₀
≧₃
₄
₃
₀
₀

₁
₀
₂
₁
₃
₁
₁
₁
₀
₃
₃
₃
－
₀
₁
₂
₀
₀
₂
₁
₀
₂
₁
₂
₀
₀

₁st-₂nd

₂nd-₃rd

Chick mortality
factor₆
₁₃Predation

₂
₀
₁

₀
₃
₂₂

Intra-speciﬁc attack

₃

₂

Infanticide₂₃b)Code no. Pair name
₂₇
₂₈
₂₉

₂₀₁₀Y
₂₀₁₁Y
₂₀₁₁S

Number of

Fledging interval (days)

eggs

nestlings

ﬂedglings

₁st-₂nd

₂nd-₃rd

₆
≧₆
₄

₅
≧₅
₄

₃
₂
₂

₀
₃
₀

₀

Infanticide
Infanticide(code ₁₀). On ₆ and ₁₅ May ₂₀₀₉ the male of pair A, theThe eggs laid by them totaled up to ₅₉ and ₂₀ chicks

owner of the neighbouring territory that failed in breed-

ﬂedged from these nests. Thus the probability of an egg

ing, ﬂied to the nest while the parents were absent andto ﬂedge is calculated as ₀.₃₄ (₂₀/₅₉).

violently attacked the ₃ nestlings after a month of hatching (see Table ₂). Although the death of one chick was
conﬁrmed later on ₁₈ May, it is highly probable that these
attacks caused its death.

Discussion
This is the ﬁrst study that evidenced existence and con-

We must be careful in calculating success rate per egg

tinuity of the pair-bond over several years by identifying

because exact information on clutch-size is available for

Oriental White Storks individually. In captive population

₁₅ (code ₂, ₄, ₇–₁₂, ₁₄, ₁₆, ₁₉–₂₃) of the ₂₆ ﬁrst clutches.

storks usually start breeding when they are four years old

48Ezaki and Ohsako: Stork breeding biology(Ogawa, ₂₀₁₁). In this study, however, a male of two

pairs, and it is possible that the artiﬁcial feeding is respon-

years old succeeded in ﬂedging a chick (clutch-code ₆)

sible also to the large clutch-size in their nests. Theseand a pair formed between birds of ₃ years old laid eggs

possibilities can be tested by experimental stops of artiﬁ-(code ₂), and males of three years old joined breedingcial feeding.

(code ₁₃, ₂₆), although pairs other than the ﬁrst one did
not ﬂedge any young.

This study suggests that predators on eggs and nestlings
come only from air, like crows and kites. This is attribut-

Information on breeding biology of the past wild popu-

able to the location of the artiﬁcial nest-towers that arelation is limited to Yamashina (₁₉₄₁). It describes clutch-

built in the open space having some, long or short dis-size usually to be ₃ or ₄ and irregularly ₂ or ₆. Results oftances from the hill. It is impossible for terrestrial preda-

our study coincides completely to his description, althoughtors to approach the nest, probably different from the past

the fact that the largest clutch size was recorded fromwild population that nested on a tree on the hill-side thatpairs regularly fed should be referred to later again. The

is accessible for mammals and snakes.

upper limit of ₅ eggs per clutch is common to descriptive

As described in results, a pair male attacked his neigh-notes by Russian and Chinese biologists (Fei ₁₉₉₁; Fei etbouring nest and is supposed to have killed a chick. It isal. ₁₉₉₁; Li et al. ₁₉₉₁; Roslyakov et al. ₂₀₀₀). Darman etsuggested that nests were invisible with each other in theal. (₂₀₀₀) who collected information using helicopters inpast wild population due to their positioning in the hill-

Amur Region describes that average clutch-size in May

side (HPOWS ₂₀₁₁). The intra-speciﬁc attack occurred

₁₉₉₈ was ₃.₄ for ₂₅ nests that is exceeded by our result

between nests near the main ﬂow of River Maruyama, andof ₃.₉ per ﬁrst clutch. The same authors describes thehence the spatial relationship of them, visibility of nests

average brood-size to be ₂.₅ in July which is almost the

could cause an easy attack.

same with the result of this study ₂.₆, excluding clutches

This study will be the ﬁrst one that reports the existencethat failed during incubation. Information on number ofof parental infanticide in the Oriental White Stork just likeﬂedglings is rare. Fei (₁₉₉₁) recorded number of eggs,

the White Stork Ciconia ciconia (e.g. Jakubiec ₁₉₉₁,

hatchlings and ﬂedglings, perhaps by a same pair for ₁₀

Tortosa and Rodondo ₁₉₉₂). Zielinski (₂₀₀₂) suggests thatyears. According to his data, ₉ chicks ﬂedged from ₁₀parental infanticide in this group of birds functions as annests, ₀.₉ per nest which is smaller than for our popula-effective measure of brood reduction in years of relativetion of ₁.₂. Thus, as long as number of eggs, chicks andfood shortage. In this study, however, ₃ of the ₄ infanti-

ﬂedglings are concerned, our population is similar to thecide occurred in nests that were fed enough, contradicting

wild Japanese population in the past, and as successful as,

the hypothesis of brood reduction. On the other hand, theor better than those breeding on the continent.

pair concerned nested at the centre of an extensive open

Concerning breeding season, egg-laying is described tospace of paddy ﬁeld, completely different from the past

start in March or April by Yamashina (₁₉₃₄), which coin-wild population. The nest is visible from all the directions.

cides completely with this study if we exclude clutches

The unnatural nest-site and food provisioning bothlaid by regularly fed pairs that started their clutches inbrought about artiﬁcially must have made the state of

February. On the continent also several authors describes

affairs surrounding the pair very complicated. Hence thisthat to be April (Fei ₁₉₉₁; Fei et al. ₁₉₉₁; Li et al. ₁₉₉₁;

subject should be studied in near future under conditions

Roslyakov et al. ₂₀₀₀).

with no artiﬁcial feeding after appropriate rearrangement

Here we should discuss the effect of artiﬁcial feedingof nest-towers.

on breeding biology of the Oriental White Stork. In thisstudy egg-laying in February was recorded only in the ₄nests by two pairs that were fed regularly. The timing of

Acknowledgements

egg-laying is greatly affected by physiological conditions

This study was supported by Grants-in-Aid for Scien-of the female, because she requires much food to produce

tiﬁc Research by Japan Society for the Promotion of Sci-

eggs (Daan et al. ₁₉₈₆). It is highly possible that the arti-

ence: Category B, ID ₂₄₃₁₀₀₃₃. Dr. Kazuaki Naito, Ms.

ﬁcial feeding stimulated too early egg-laying of the two

Kayo Horina and Ms. Megumi Tanibuchi of Hyogo Park

49

Reintroduction（2012）2: 43 – 50of the Oriental White Stork helped us in making tables
and ﬁgures. We are grateful to all of them. Thanks are also
due to anonymous referees.

Shoten, Tokyo. (in Japanese)
Zielinski P (₂₀₀₂) Brood reduction and parental infanticide – arethe White Stork Ciconia ciconia and the Black Stork C.
nigra exceptional ? Acta Ornithologica, ₃₇: ₁₁₃ – ₁₁₉.

(Accepted: ₁₅ December ₂₀₁₂)

References
Daan S, Dijkstra C, Drent R, Miejer, T (₁₉₈₆) Food supply andthe annual timing of avian reproduction. Acta XIX Congressus Internationalis Ornithologici, ₃₉₂ – ₄₀₇. University ofOttawa Press. ₁₄₀₀ p.
Darman YA, Andronov VA, Parilov MP, Higuchi H, NagendranM, Kirichenko YI (₂₀₀₀) Status of Oriental White Stork
population in Amur region. In Litvinenko NM (ed) Oriental
White Stork in Russia. Russian Academy of Sciences Far
Eastern Branch, Vladivostok. pp. ₂₀ – ₂₄. (in Russian withEnglish summary)
Fei D (₁₉₉₁) The breeding of one pair of Oriental White Storks
in the outskirts of Qiqihar, Heilongjiang Province. In Coulter
MC, Wang Q, Luthin CS (eds) Biology and Conservation of
the Oriental White Stork Ciconia boyciana. Savannah River
Ecology Laboratory, Aiken, South Carolina USA. pp. ₅₉ – ₆₃.
Fei D, Ping W, Wu G, Wu T, Xiu T (₁₉₉₁) Observations on thebreeding biology of the Oriental White Stork (Ciconia boyciana) near Qiqihar, Heilongjiang Province, China. In Coulter MC, Wang Q, Luthin CS (eds) Biology and Conservationof the Oriental White Stork Ciconia boyciana. SavannahRiver Ecology Laboratory, Aiken, South Carolina USA. pp.
₂₁ – ₃₀.
HPOWS (Hyogo Park of the Oriental White Stork) (₂₀₁₁) The
Grand-Design for the Reintroduction Project of the Oriental
White Stork. Hyogo Prefecture, ₃₆ p. (in Japanese)
Iwasa S (₁₉₃₆a) Kounotori. Bulletin of the Hyogo Natural History Society, ₁₁: ₂₁ – ₂₇. (in Japanese)
Iwasa S (₁₉₃₆b) Kounotori (Ⅱ). Bulletin of the Hyogo Natural
History Society, ₁₂: ₅₉ – ₆₁. (in Japanese)
Jakubiec Z (₁₉₉₁) Causes of breeding losses and adult mortality
in White Stork Ciconia ciconia in Poland. Studia Naturae,
₃₇: ₁₀₇ – ₁₂₄.
Li W, Zhao H, Luan X (₁₉₉₁) Reproductive ecology of the Oriental White Stork (Ciconia boyciana) with information on
feeding and development of the chicks. In Coulter MC,
Wang Q, Luthin CS (eds) Biology and Conservation of the
Oriental White Stork Ciconia boyciana. Savannah River
Ecology Laboratory, Aiken, South Carolina USA. pp. ₄₇ – ₅₈.
Ogawa H (₂₀₁₁) ₂₀₁₀ International Studbook for the Oriental
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50

再導入されたコウノトリの繁殖期と繁殖成功，および給餌と人工巣塔の影響* 江崎保男1,2・ 大迫義人2₁

兵庫県立大学自然・環境科学研究所生態研究部門／兵庫県立人と自然の博物館
₆₆₉-₁₅₄₆₂兵庫県三田市弥生が丘 ₆

兵庫県立大学自然・環境科学研究所田園生態保全管理
研究部門／兵庫県立コウノトリの郷公園
₆₆₈-₀₈₁₄

兵庫県豊岡市祥雲寺₁₂₈* E-mail:摘要
兵庫県但馬地方でコウノトリの野生復帰が開始されたのは₂₀₀₅年のことであり，個体数は野外繁殖の成功とともに増加している．当該個体群は個体識別されており，
コウノトリのペアはいったん繁殖すると同じ場所で相手を変えず繁殖し続けること，つまりつがいのきずなが続くことが証明された．₂₀₀₇年から₂₀₁₁年の ₅ 年間に ₈ ペアが，失敗後のやり直しの ₃ クラッチを含めて₂₉クラッチを産んだので，これに対して定量的な解析を行なった．その結果，抱卵期と育雛期がそれぞれ₃₁-₃₅日と₆₃-₇₄日であり，産卵開始から最初のヒナが巣立つまでに
おおよそ₁₀₀日を要すると結論できる．また，産卵期は ₃月上旬から ₄ 月下旬，ヒナの巣立ち期は ₆ 月中旬から ₇
月下旬の間であった．いっぽう十分な給餌を受けていたペアの産卵と巣立ちは例外的に早かった．クラッチサイ
ズはほとんどが ₃ もしくは ₄ であり，例外的な卵数 ₆ は十分な給餌を受けていたペアのみで記録された．ヒナの死亡はトビによる捕食と隣接ペアによる襲撃によって起こったが，親による子殺しが ₃ 巣で見られ，これにより₄ ヒナが死亡した．給餌と人工巣塔上での営巣およびその配置はコウノトリの繁殖生態に大きな影響を与えており，十分な給餌を受けているペアで子殺しが多く起きたので，これに関与する要因は複雑であると考えられる．
キーワード

繁殖期，コウノトリ，クラッチサイズ，子殺し，つがいのきずな，野生復帰