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33

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35

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93

速報

事例にみる街路樹の点検・診断の現状
飯塚康雄1, *・舟久保敏1

表 1.

I． は じ め に
街路樹は，植栽後から長期間経過したことにより大径木化・衰弱化が見られるものが増加し，台風などの強風いる．このような状況の中で，街路樹整備に関する技術的指針である「道路緑化技術基準」が平成 27 年 3 月 31日に改正され，道路交通の障害などを未然に防止しつつ街路樹に求められる機能を総合的に発揮させるために必ヒアリング調査時には一部に倒伏や落枝による交通障害などを起こして要となる安全点検が具体的に位置づけられた．しかし，街路樹の点検・診断方法は，道路における街路樹の位置
づけ（求める緑化機能）や植栽環境，管理体制や予算規一律に決められるものではない．そのため，道路管理者
が今後事業化を図る際の参考となるよう先進事例について調査し，点検・診断方法の類型化を行い，実施項目，
体制等について整理，把握した．

II． 調 査 方 法
調査は，全国から抽出した街路樹の点検・診断に取りアンケート調査

模，地域によっては住民感情などにより大きく左右され，調査対象とした道路管理者と点検・診断

道路管理者

街路樹本数

開始
年度

契機となった
障害

札幌市
仙台市
東京都
東京国道事務所
神奈川県
京都市
大阪市
吹田市
尾道市
福岡市

約 22 万本
約 5 万本約 60 万本
約 2.2 万本
約 1.6 万本
約 4 万本約 16 万本
約 0.9 万本
約 0.2 万本
約 5.5 万本

H24
H22
H10
H24
H27
H22
H27
H26
H26
H24

ポプラ倒伏など
ケヤキ倒伏
ケヤキ倒伏
−
近隣での倒伏−ケヤキ倒伏−
近隣での倒伏
ケヤキ倒伏

帯広市
横浜市
相模原市
新潟市
名古屋市
西宮市
広島市
日田市
那覇市

約 3 万本約 13 万本
約 1.2 万本
約 3.6 万本
約 10 万本
約 2.2 万本
約 3.6 万本
約 0.1 万本
約 1.3 万本

H25
H26
H20
H27
H14
H27
H27
H27
不明

−
ユリノキ倒伏不明
不明
プラタナス倒伏
近隣での倒伏−ケヤキ倒伏−* 札幌市と東京国道事務所は現行の点検 ･ 診断の改定年度．

組んでいる道路管理者（表 1）に対してアンケートとヒ
アリング形式により行った．調査内容は，①基本的事項

巡回・定期巡回・異常時巡回をして，診断では簡易診断，として点検目的，方針，マニュアル等の整備状況，②点

腐朽率等の機器診断を含む樹木健全度調査，植栽環境調

検 ･ 診断方法として点検項目，点検票，③体制として点査，
剪定等の作業時における異状確認などを行っている．

検手法，点検者資格要件，頻度，そのほかに異状木の措

これらを類型化すると，管理対象となる街路樹の位置づ

置，精度確保策，実施の効果等とした．

け及び樹種や樹形，植栽環境，予算規模等に応じて，主III． 結果と考察に点検・診断の実施内容と実施者の違いにより，詳細型・標準型・簡易型の 3 タイプとなった（表 2）．実施にあたっ

街路樹の点検 ･ 診断は，平成 10 年度に東京都が着手ての指針やマニュアル類としては，管理者独自で策定さしたのを始まりとして，最近の 10 年間にはポプラ，ケ

れているもののほか，先行自治体のものが活用されていヤキ，ユリノキ，プラタナス等の倒伏を契機に，大都市た．点検・診断の実施者としては，
自治体などの職員（造を中心に拡がった（表 1）．道路管理者は点検では通常

園，土木），緑地管理業者，樹木医が選定されており，

Yasuo Iizuka1, * and Satoshi Funakubo1（2018）A case study on the current state of inspection and diagnosis of street
trees. Tree and Forest Health 22 : 93〜94* 責任著者（Corresponding author）E-mail：iizuka-y92dh@mlit.go.jp
1
国土交通省国土技術政策総合研究所
1
National Institute for Land and Infrastructure Management※ 樹木医学会は記事中の材料および方法を個別に推奨するものではありません．本記事は樹木医学会第 22 回大会におけるポス
ター発表の内容です．

37

94

樹

木

医

学

研

究

第 22 巻

2 号 （2018）

表-2． 類型別の街路樹点検・診断の内容方法，手順，診断項目

点検・診断精度の確保として実施要領などの作成や講習

かで，診断項目の固定化や診断機器の普及が進んでおり，

会・研修会の開催，複数人による点検・診断等が行われ樹木医などの有資格者に限らず行えるものになりつつあていた．点検 ･ 診断結果を受けた措置は，主に剪定と伐る．そのなかで，景観向上，緑陰，環境保全などの街路

採で，補植される場合もあった．実施の効果としては，樹の機能を発揮させるには大きいことも重要で，健康に倒伏などによる事故が減少したという回答があった．点

長寿化させる管理方法の基礎データとして点検・診断結

検・診断結果は，倒伏・落枝を未然に防止する措置を決果を活用すべきである．さらに，蓄積された点検・診断定するための根拠として利用されるほか，データベース

データにより示すことが可能な不健全となりやすい樹種化して新たな管理方針策定への活用などに展開したい意

や樹齢などの特徴は，点検・診断の計画立案時における向があるものの，組織の人員や予算などの制約から実施

実施時期や優先樹種，診断項目等の設定に活用することまでには至っていない現状がうかがえた．

で，街路樹の点検・診断の高度・効率化に繋げることがIV． まとめと今後の課題
街路樹の点検 ･ 診断が実施されていることにより，倒伏 ･ 落枝による交通障害などは減少しているものの，点検・診断結果は伐採の可否を判断するためだけの根拠として活用されていることがほとんどであった．
そのため，樹木医などの資格を持たない職員でも，点検・診断前の研修と試行経験により樹体の構造的な弱点（以下，弱点とする）を認識でき，街路樹の危険性を排除することが可能となっていた．
街路樹診断は，開始されてから 20 年程度経過するな

38求められる．また，弱点というマイナス評価により伐採の可否に終始しがちな点検・診断に，弱点を補強する構造の評価や街路樹本来の機能などのプラス評価を加え，積極的な保全措置を検討すべきである．

引

用

文

献

国土交通省（2015）「道路土工構造物技術基準」の制定及び「道路標識設置基準」，「道路緑化技術基準」の改正について．
http://www.mlit.go.jp/report/press/road01_hh_000495.
html （2017 年 12 月 14 日閲覧）（2017 年 12 月 15 日受理）

:DWHUELUG6RFLHW\㸦Ỉ㫽Ꮫ఍㸧ᅜ㝿ㄅ :DWHUELUGV㸦㸧㸦㸧㸸

Site Fidelity in Lineages of Mixed-species Heron Colonies
MIYUKI MASHIKO1,2,* AND YUKIHIKO TOQUENAGA1
1

Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai,
Tsukuba, Ibaraki, 305-8572, Japan

2

Current address: National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure,
Transport and Tourism, 1 Asahi, Tsukuba, Ibaraki, 305-0804, Japan*

Corresponding author; E-mail: mashiko@pe.ies.life.tsukuba.ac.jp

Abstract.—As heron and egret colonies are sometimes abandoned due to human activity and subsequently
newly established at nearby locations, colony locations per se cannot represent colony fates. Here, “colony lineages”
were traced by connecting short-distance location shifts between colony sites in consecutive years to quantify thesite ﬁdelity of heron colonies themselves rather than the breeding-site ﬁdelity of individuals. Site ﬁdelity of 61
colony lineages recorded from 1963 to 2013 in and around Ibaraki Prefecture, Japan, was evaluated by persistence
periods with survival analysis and shapes of historical trajectories by applying the correlated random walk analysis.
While 36% (n = 22) of colony lineages did not show site ﬁdelity and lasted only 1 year or indicated untangled shapesof historical trajectories, 64% (n = 39) of colony lineages exhibited site ﬁdelity by reusing the same locations for
multiple years or by staying within a small area with entangled shapes of historical trajectories. Even though suitablebreeding sites were abundant in the study area and site ﬁdelity of colony members was low, a high rate of site ﬁdelity in colony lineages may be achieved when a few faithful pioneer herons and egrets are followed by many others.
Received 12 June 2017, accepted 15 January 2018.
Key words.—Ardeidae, colony lineage, correlated random walk, egret, heron, site ﬁdelity, trajectory.
Waterbirds 41(4): 355-364, 2018

Breeding-site ﬁdelity is common to mostbird species that form colonial breedingsites (Cézilly et al. 2000; Bried et al. 2003).
Colonial herons and egrets (Ardeidae) canform colonies on trees, bushes, reeds andthe ground in inland areas, and their colonies often persist at the same locations formany years (Kushlan and Hancock 2005).
However, some heron colonies exist for only
one or at most a few years, and others shift toneighboring locations (Bancroft et al. 1988;
Kelly et al. 2007). Such colony abandonment and relocation are sometimes causedby human disturbance because the noise
and unpleasant odors of heron colonies canbe disagreeable and annoying for residents
when they are located near residential areas(Hafner 2000; Telfair et al. 2000; Parkes et al.
2012).
Solving such conﬂicts between humanresidents and avian breeding colonies requires knowledge of how these colonies
are formed and persist at speciﬁc locations.
Research on species distribution and habitat selection may provide insights into thedevelopment of appropriate ecologicalapproaches for tackling these problems(Parkes et al. 2012), but research has con-ventionally focused on the philopatry orsite ﬁdelity of individuals within persistingcolonies (Atwood and Massey 1987; Aebischer 1995; Vergara et al. 2006). However,avian colonies are often formed with individuals that are not highly philopatric. For
example, the frequency with which individual herons and egrets return to their natal
or previous breeding locations was 55% at
most (Fernández-Cruz and Campos 1993;
Melvin et al. 1999; Fasola et al. 2002). These
colonies were annual, or only formed during the breeding season within a year. Thus,
colonies with site ﬁdelity are reformed withdifferent members annually at exactly thesame locations. Moreover, colonies can be
relocated to nearby sites when human beings force the birds to evacuate former colony sites by completely destroying nesting
resources. For such colonies, the site ﬁdelity of colonies themselves rather than thebreeding-site ﬁdelity of individuals can beused to solve conﬂicts between human residents and colonial avian species.
As colonies are relocated due to humanactivity and other causes, colony locations per
se cannot represent colony fates. Therefore,“colony lineages” can be traced by connect-

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39

356

WaTerbirds

ing multiple colony sites for each colony history (Garden 1958). Colony abandonmentis often followed by the establishment of a
new colony at a nearby location, and suchnew sites should be considered descendantsof the abandoned colonies rather than newcolonies (Mashiko and Toquenaga 2013).
Site fidelity of moving colonies should be
defined based on the frequency of relocation, persisting period of each colony site,
and the shapes of the trajectories of relocation events.
Our objectives were to quantify the site
fidelity of heron colony lineages based on
their historical trajectory, or the consecutive movement path of colony sites within alineage. We analyzed 51 years of colony data
for the northern Kanto Plain, Japan. Since
the breeding and foraging habitats are homogeneously distributed (Carrasco et al.
2014, 2015) and human disturbance occurs
frequently in the area, we hypothesized thatcolony lineages with site fidelity should becharacterized by: 1) not one-year but rather
multiple-year persistence periods; and 2)
not untangled but rather entangled shapesof historical trajectories.
MeThods
Study Area
This study focused on 11,865 km2 in Japan in a region that included the Ibaraki Prefecture and borderedon the regions of Fukushima, Tochigi, Saitama andChiba Prefectures in the northeastern part of the Kanto
Plain, Japan (35° 53ʹ N to 36° 54ʹ N, 139° 41ʹ E to 140°49ʹ E; Fig. 1). The north is mountainous and not suitable habitat for herons and egrets. The remainder ofthe region is flat lowland with large areas along rivers
used for rice production and lotus fields scattered near
Lake Kasumigaura. The flooded fields and irrigation
ditches support large numbers of foraging herons andegrets (Lane and Fujioka 1998). Breeding habitat washomogeneously distributed here; when we gridded theentire study area into 915-m x 915-m cells, 94.5% of thecells contained at least one pixel (45.7 m x 45.7 m) oftrees or bamboo, primarily moso bamboo (Phyllostachys
pubescens), Simon bamboo (Pleioblastus simonii) or dwarf
bamboo (P. chino), thickets that are potential breedingsites for herons and egrets (Carrasco et al. 2014, 2015;
Fig. 2). Residential areas were also scattered throughout
the lowland, and human disturbance occurs frequently
where heron and egret colonies are located adjacent toresidential areas (Fig. 2).

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40

Every year, the herons and egrets breed mainly inmixed-species colonies from March to August: Grey
Heron (Ardea cinerea) arrives first in March; Great
Egret (A. alba), Little Egret (Egretta garzetta) and Blackcrowned Night-Heron (Nycticorax nycticorax) arrive in
April; Intermediate Egret (A. intermedia) arrives in late
April; and finally, Cattle Egret (Bubulcus ibis) arrives by
early May. Colony size varied considerably, from approximately four to over 3,000 individuals (Environmental
Agency of Japan 1994; Mashiko and Toquenaga 2013).
Intermediate and Cattle egrets are summer migrant
species, but the other four species are a mixture of residents and migrants in the area, and some individuals
winter in this area. Until the early 1990s, some colonysites were also used for roosting by wintering Great andLittle egrets from September to February (Anzai 1990);
however, since 1995, all colony sites have been used only
for breeding by the six species, and all colonies become
vacant by October.
Colony Data
Colony sites in the study area from 1963 through2013 were included. The most intensive surveys wereconducted from 1999 to 2013 (annual number of colony sites = 22.0 ± 1.1) during which we obtained colony
location data from region-wide aerial and ground-based
searches. Aerial censuses were conducted from 1999
to 2000 using aircraft (Fujioka et al. 2001) and from2002 to 2013 with aerial photography using a radiocontrolled paraglider (Mashiko and Toquenaga 2013).
For ground-based searches, colony sites were found bychecking the places in which colonies had been locatedin previous years, and all colony sites were surveyed atleast once in a breeding season. When a colony wasabandoned, searches were made to determine whether
other colonies had formed nearby. From 1983 to 1998
(annual number of colony sites = 17.5 ± 0.9), we obtained colony location data from ground-based searches(Koshida 2007). We obtained colony location data fromlocal literature and personal communications with local
amateur avian observers before 1983 (annual numberof colony sites = 3.3 ± 0.5). We also complemented thedata with literature and interviews from 1983 and later
to minimize the number of colony sites not detected.
Our focus was on colony lineages, and we needed asmuch documented history for each colony as possible
over a long period. Thus, we included all known colonysites since 1963 even though some colonies prior to1999 may have been undetected. Preliminary examination showed that the results of analyses excluding dataprior to 1999 did not differ from those using the entire
dataset.
Confirmation of Colony Lineages
To determine colony lineages, first we documented the year and location of establishment, persistence,
and abandonment of each constituent colony site. A
colony site was deemed abandoned when it was confirmed that no breeding activities were conductedin the following year at the location of the previous
year’s colony site. A colony site was deemed newly es-

SITE FIDELITY IN HERONRY LINEAGES

357

Figure 1. Map showing the location of 61 colony lineages in the study area around Ibaraki Prefecture, Japan, from1963 to 2013. Broken lines represent prefectural boundaries, and continuous lines represent the main rivers in the
study area. Enlarged ﬁgures of mobile lineages (no. 4, 38, and 54) showing different shapes of trajectories are included below the map. The diameters of the circles reﬂect the persistence period of each colony site. Pref. = Prefecture.

tablished when breeding activities were conﬁrmed at alocation where there had been no colony in the previous year. When we could not determine the existenceof a colony at a speciﬁc site in one year (year t), we ﬁrst
conﬁrmed its presence in previous years (t − k, 0 < k) as
well as in the subsequent year (t + 1). If the site’s presence could be conﬁrmed both before and after year t,
it was considered present in year t − i as well where 0) i ) k. Conversely, even if the colony was conﬁrmed
both before and after the year t, when we were able
to positively conﬁrm that a colony site did not exist
in year t, we treated the colony that lasted until t – k
and the colony established in t + 1 as separate. To determine the persistence period for each colony site,
the number of years from the ﬁrst establishment at alocation was counted.

We evaluated colonies based on lineage, rather
than the observed colony sites themselves, to accountfor short-distance location shifts. When abandonment
and new establishment occurred in neighboring locations in successive years, the new site was assumed to
be a descendant of the abandoned one. This is supported by the behavior of heron and egret individuals
at the beginning of their breeding season when theychoose their colony site: if a site has become unsuitable
for nesting through the natural death of vegetation or
human-induced disturbances, herons and egrets ﬁrst
circle above the location of the colony site it had used in
the previous year. They sometimes ﬂy away, but at othertimes they stay on trees nearby and, ﬁnally, this nearby
location becomes a new colony site (M. Mashiko and Y.
Toquenaga, pers. obs.; Fig. 2). To determine a reason-'RZQORDGHG)URPKWWSVELRRQHRUJMRXUQDOV:DWHUELUGVRQ
7HUPVRI8VHKWWSVELRRQHRUJWHUPVRIXVH

41

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WaTerbirds

Figure 2. Enlarged map showing trajectory of lineage no. 27 with its observed causes of abandonment of constituent colony sites.
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42

SITE FIDELITY IN HERONRY LINEAGES
able maximum distance for colony-site shifts included
within a single lineage, we calculated mean nearestneighbor distance from the center of observed colonysites (11.85 ± 1.76 km; 1999-2013), and it was assumed
that each colony had a circular domain within which
foraging herons and egrets belonged to the colony. The
radius of the domain of attraction was set to be half theaverage nearest-neighbor distance (5.93 km; Mashiko
and Toquenaga 2013). Since our focus was site ﬁdelity
at the colony level, we deﬁned colony lineages regardless of whether the colony site at year t was composed of
the same or different birds at year t − 1.
To detect which lineages exhibited site ﬁdelity, we
ﬁrst focused on the persistence periods for lineages
and classiﬁed them into two categories: “one-year” and“multiple-year”. For multiple-year lineages, which may
indicate site ﬁdelity, we focused on the number of colony sites that the lineage had used and classiﬁed theminto two categories: “mobile”, which includes at least
one location shift, and “stationary”. To determine how
many lineages in these two categories exhibited site ﬁdelity, we performed the following analyses.
Measuring Site Fidelity of Colony Lineages
For stationary lineages, being stationary alone did
not indicate site ﬁdelity. For instance, when we compared site ﬁdelity of a stationary lineage that persisted
for 2 years with a mobile lineage that included two colony sites that existed for only 1 year and that persisted for
3 years, it could not simply be determined that the stationary lineage that persisted for 2 years exhibited site
ﬁdelity. To examine whether stationary lineages exhibited site ﬁdelity, we compared persistence periods forsites of stationary lineages with those for sites of mobile
lineages. Persistence periods for sites of mobile lineages
were used as the null expectations for this comparison
because if the persistence periods of stationary lineages
were shorter than the average of those of mobile lineages, it would be difﬁcult to assert that stationary lineages
exhibited site ﬁdelity. Since the datasets for persistence
periods contained censored data (an abandonment
event of a colony site was not observed before the endof our study period), non-parametric survival curves
were estimated for each category with the Kaplan-Meiermethod in the survival analysis (Kleinbaum 1996). Differences between the curves were evaluated with the
log-rank test.
To investigate whether the mobile lineages exhibited site ﬁdelity, we examined colony trajectories (i.e.,the consecutive movement path of colony sites within alineage) by applying a correlated random walk method(Kareiva and Shigesada 1983) at the colony level. Since
the shapes of trajectories are considerably different
among lineages even if those lineages are composed of
the same number of colony sites and movements (e.g.,lineages #4 and #38 in Fig. 1), we considered a mobile
lineage to exhibit site ﬁdelity if the trajectory remained
within a small area (entangled), and to not exhibit site
ﬁdelity if the trajectory was increasingly distant (untangled) or intermediate between entangled and untangled (border). To clarify which trajectories were entan-359

gled and which were untangled, we developed an index
of the distance between a focal point and the last site ofa trajectory (DFL), and compared those values to theobserved and expected trajectories. DFL is inspired by
net squared displacement, which is widely used for analyzing the movement patterns of mammals (Bergman etal. 2000) and insects (Brouwers and Newton 2010), as
well as growth in plants (Cain 1990).
We calculated the DFL of observed trajectories. The
focal point was a location at which the weighted sum of
the distances from all given colony sites in a trajectorywere minimized. We obtained this point using the zsummin function in the statistical program R package orloca(Fernandez-Palacin and Munoz-Marquez 2012), which
deals with the Fermat-Weber location problem. Weighting was based on the persistence period of each colonysite. For each observed trajectory, we constructed 100
expected trajectories by choosing a length and turning
the angle randomly from all segments of all mobile trajectories as many times as the length of persistence period of the observed trajectory (n = 517, length: ranged
from 0 to 5,908.6 m (482.7 ± 53.5 m), turning angle:
ranged from −177° to 167.5° (0 ± 1.9°)). When a sampled length or turning angle forced the movement intoa body of water or mountainous region (gray regions in
Fig. 3), we sampled another length or turning angle so
as to construct expected trajectories within a geographical range where colonies could be formed (white regions in Fig. 3). Finally, we compared the observed DFL

Figure 3. Map showing a geographical range where
heron colonies could be formed. For constructing expected trajectories of mobile lineages, white areas indicating lowlands with an altitude of 0 m to 100 m, where
heron colonies could be formed in trees and bamboo
thickets, were used but gray areas indicating mountainous regions (> 100 m) or deep bodies of water were notused. Pref. = Prefecture.

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43

360

WaTerbirds

with the mean DFL of randomized trajectories to examine the entanglement of observed trajectories. We identified entangled and untangled trajectories when the
DFL of the observed trajectory was respectively smaller
and larger than the 95% confidence limits of those of
the randomized trajectories. Trajectories that fell within
the 95% confidence limit were classified as border.
Some colony lineages may have multiple trajectories: when a lineage contained more than one colonysite in the same year, the trajectory diverged into different paths (e.g., lineage #54 in Fig. 1). Similarly, originally unique trajectories could be joined when colony sites
from two trajectories were abandoned in the same year
and, in the following year, a single colony site was newly
established in a location near both the abandoned sites.
However, even if a lineage contained more than one
colony site in the same year, we used the larger, majorcolony site to make a single trajectory so as to avoid
making too many trajectories when reliable data for thecolony sizes of those sites were available (Mashiko andToquenaga 2013). We examined the entanglement for
all trajectories using DFL, but judgment of entanglement of multi-trajectory lineages was made for each colony lineage rather than each trajectory: the lineage wascategorized as untangled, border, or entangled when
the judgment of all trajectories was the same, and it wasdeemed border when the judgment differed among tra-jectories. All statistical analyses were conducted with statistical program R (R Development Core Team 2013).
Where appropriate, we report mean ± SE.

resulTsDuring the 51-year period from 1963 to2013, a minimum of 163 colony sites were used
for at least one breeding season in the study
area (Fig. 1). This included seven colony sitesthat were re-established at exactly the same location after their abandonment. The recorded
163 colony sites were categorized into 61 lineages. While 10 out of 61 lineages (16.4%) existed for only 1 year (open circles in Fig. 1), theremaining 51 lineages persisted for more than
1 year (Fig. 4A). These 51 multi-year lineages
were composed of 26 mobile and 25 stationary
lineages (Fig. 4B). Mobile lineages were composed of 127 colony sites. Stationary lineages
were composed of 26 colony sites because one
lineage had two colony sites within a 5.93-km

Figure 4. Summary of the classification of 61 lineages. Values represent the number of lineages. White, light grayand dark gray sections represent no site fidelity, border, and site fidelity, respectively.

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44

SITE FIDELITY IN HERONRY LINEAGES

radius in the same year. Survival curves differed between colony sites of stationary lineages and null expectations: persistence periods of colony sites in stationary lineages weremuch longer than those in mobile lineages (r2= 14.4, P < 0.001; Fig. 5). Thus, the stationary
lineages exhibited site ﬁdelity by reusing thesame site for many years.
The 26 mobile lineages were composed of
39 trajectories because ﬁve out of 26 lineages
had multiple trajectories. The number of colony site shifts in a lineage ranged from one tonine (3.1 ± 0.29). Results of entanglement oftrajectories evaluated based on DFL revealed
that six lineages were above the line of equality for observed and expected DFL, six wereborder, and 14 were below (Fig. 6). Hence,four lineages were untangled, but 14 lineages (53.8%) were entangled (Fig. 4C). When
those results were combined with one-yearand stationary lineages, 22 lineages (36.1%)
did not exhibit site ﬁdelity, but 39 lineages(63.9%) did (Fig. 4D).
DISCUSSION
Lineages of heron and egret colonies demonstrated that these species had a preference
for reusing the same or nearby sites as in previ-

Figure 5. Survival curves of the persistence period of
the colony sites using the Kaplan-Meier estimate. The
broken line represents colony sites that constituted
mobile lineages (n = 127), and the solid line represents
those that constituted stationary colony lineages (n =26). Vertical bars represent censored observations.

361

ous years even though breeding sites are widely
available throughout the study area. One possible explanation of the mechanism behindsite ﬁdelity is that herons and egrets have ﬁdelity to foraging sites as well as to colony sites(Yamada 1994), and thus subsequently selectcertain locations as colony sites. Food availability, measured as the area of potential foraging habitat around the colony, has often beenthought to be the most important factor affecting the location and size of a heron colony (Fasola and Barbieri 1978; Gibbs 1991). However,variables related to foraging sites did not havea major impact on locations and sizes of colonies in our study area (Fujioka et al. 2001; Tohyama 2005; Carrasco et al. 2014, 2017). Thus,
the site ﬁdelity of colony lineages is not merely
caused by individuals’ preferences for foraging
habitats.
The frequency of return to natal or previous breeding locations has been well studied in colonial seabirds (Atwood and Massey
1987; Spendelow et al. 1995), but only threestudies have assessed it in herons and egrets.
Fernandez-Cruz and Campos (1993) banded
Grey Heron ﬂedglings (n = 319) at a colony
in Spain over 5 years, with an 11.6% return tothe colony the following year, 5.6% return after 3 years, and 3.1% return after 4 years. Melvin et al. (1999) measured natal site ﬁdelity in
the USA from a dataset spanning from 1914
to 1994 with 16.2% for Great Blue Herons (A.
herodias), 23.8% for Great Egrets, 18.0% for
Snowy Egrets (E. thula), 7.9% for Little Blue
Herons (E. caerulea) and 12.5% for Tricolored
Herons (E. tricolor). Fasola et al. (2002) investigated the dispersal rate of Little Egrets incolonies in the Camargue in southern France.
They marked 6,618 chicks and 504 adults over
16 years and found an average estimated dispersal rate among colonies of 45%; in otherwords, 55% of individuals seemed to exhibit
natal- or breeding-site ﬁdelity. These low average individual site ﬁdelities seemingly contradict our results showing that nearly two thirdsof heron colony lineages exhibited site ﬁdelity.
A high degree of site ﬁdelity at the colonylevel may occur when a few faithful individuals return to a colony site and many others
follow them. Generally, frequency of breedingsite ﬁdelity is higher in males than in females'RZQORDGHG)URPKWWSVELRRQHRUJMRXUQDOV:DWHUELUGVRQ
7HUPVRI8VHKWWSVELRRQHRUJWHUPVRIXVH

45

362

WaTerbirds

Figure 6. Comparison of observed and expected trajectories by distance between focal point and last colony site
(DFL) of 26 mobile lineages. Each circle represents a trajectory. ID of the lineage and trajectory corresponds toFigure 1. Letters represent multiple trajectories in a lineage: lineage #18, 37, 43, 45 and 54 had 3, 5, 6, 2 and 2 trajectories, respectively. The broken line represents the line of equality. Trajectories were categorized into untangled(open), entangled (filled), and border (gray). Each circle with a line represents the exact value for observed trajectory and mean with a 95% confidence interval for the expected trajectory.

among bird species (Greenwood 1980; Shields
1982), the rate of nest- or colony-site fidelity
is higher in adults than in juveniles (Haymes
and Blokpoel 1978; Aebischer 1995), and theexperience of breeding success at a colony site
could also enhance fidelity to that location(Vergara et al. 2006). In our case, a proportionof male, adult or resident herons and egrets
may have been familiar with colony locations.
Those individuals may have exhibited colony-site fidelity and taken the initiative in thecolony site selection at the beginning of every
breeding season.
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46

While other nomadic individuals, suchas females, juveniles, dispersive adults andmigrant species, may not exhibit fidelity to a
specific colony site, they may be cued by thepresence and abundance of conspecifics orhetero-specifics when choosing where to settle
and thus contribute to a high degree of site fidelity at the colony level. This mechanism is
expected to operate broadly in the breedinghabitat patch choice of social animals like colonial birds (Forbes and Kaiser 1994; Toquenaga
et al. 1995; Serrano et al. 2003). Herons andegrets also refer to the presence of other spe-

SITE FIDELITY IN HERONRY LINEAGES

cies as a source of information for choosing
their colony sites (Belzer and Lombardi 1989).
Site ﬁdelity or dispersal of individuals may beinﬂuenced by the status of their colonies, aswith allee effects of colony size in colony site
selection of individuals (Serrano et al. 2005).
Conversely, about one third of colony lineages did not exhibit site ﬁdelity. There is apositive correlation between an individual’s
reproductive success and its subsequent nestor colony-site ﬁdelity (Vergara et al. 2006), andﬁrst-year breeders or immature birds rely on
the reproductive successes of nesting adults toassess their own chances of breeding successfully in a given patch and to make settling decisions (Danchin et al. 1998; Schjørring et al.
1999; Calabuig et al. 2008). Heron and egret
individuals that had bred at single-year colonies may be less likely to recruit follower individuals because they may have suffered lowered reproductive success, due to any numberof factors including human disturbances, andmoved to different colonies the following year.
Site ﬁdelity was observed in more than halfof mobile lineages, and it could have originated from a few faithful pioneer individuals
with many others following them. Even whenheron colonies shift their locations to alternative sites, mobile colony lineages tend to staywithin a small area rather than moving far
away unless some unsuitable condition, suchas human disturbances, overrides the ecological advantages of site ﬁdelity. For mobile
colony lineages with an entangled trajectory,
management techniques should be developed
to retain colonies at locations where conﬂictwith neighboring humans can be minimized.
A historical perspective of colony lineages isnecessary so as not to become trapped in a
vicious circle of conﬂict, and the applicationof random walk models by considering the
trajectories of mobile bird colony lineages as
movement paths of an individual looking forsuitable locations is useful for examining thesite ﬁdelity of gregarious animals at the colonylevel.
ACKNOWLEDGMENTS
We thank K. Hikosaka, T. Anzai, S. Ohshio, N. Tanigaki, R. Yamagishi, T. Tohyama, T. Yamaguchi, C. Koshida, H. Takeda, A. Abe, K. Nabeya, and L. Carrasco363

for colony censuses from 1983 to 2013. We are deeply
indebted to M. Fujioka for supplying colony researchdata in the study area from 1996 to 2000, and S. Ikeno
for supplying reports of colony censuses in 1995-1996,
2000-2001, 2005-2006 and 2008 that were carried out by
the Wild Bird Society of Japan, Ibaraki branch. We are
grateful to T. Kawasaki, S. Kasuga, T. Uetake, R. Saito,
M. Seido, K. Takeda, K. Ueda, M. Yamaguchi and thecolonies’ neighbors for supplying information or local
literature about the locations and histories of some colonies. We also thank K. Fujii, K. Ohashi and membersof the Population Ecology Laboratory for helpful discussions. This study was partly supported by the Global
Environment Research Fund (F-1) from the Ministry of
the Environment, Japan, and by JSPS KAKENHI Grant
Numbers 13740433, 19570014 and 26440233. All applicable ethical guidelines for the use of birds in research
have been followed.
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੃৘प೜કखथःॊ

‫ٴ‬+ِ෤भ੦মੑ઺पउऐॊে੟੗஘ਙभન৳पঢ়घॊૼ୒৓ଦൟহඨّ

َ੃৘કড়ऋে੟੗஘ਙभ
੎ਏਙ॑৶ੰघॊऒधऋ‫ؚ‬੃৘टऐदऩऎ‫ؚ‬৉ૉ৸৬भে੟੗஘ਙभ
৳৸प੎ਏُ
‫ق‬ीएौभःऌुभ‫ك‬ಞ੧‫ٴ‬+ِ੃৘भে੟੗஘ਙभ੐ఏ‫ق‬ಞ੧‫ّك‬َ਌ਏऩ৉ୠभেଙ௺ऋோ૔घॊ৉ਡपেඅྼमে୘घॊர॑
জই॓ঞথ५ர‫ق‬੐ఏர‫ك‬धखथਝ৒ख‫ؚ‬जभ૗৲॑઴৒घॊُ

َ৿೘੟भেඅ‫؞‬ে୘૾யपঢ়घॊેীऩॹ‫॑ॱش‬થघॊঽ੘৬ऋாीथ૘ऩःُ ‫ق‬বଅઐৢ੄ +ҩ৹ਪ੥ટ‫ك‬‫ق‬বଅઐৢ੄ +੃৘धে੟੗஘ਙ
ঃথইঞॵॺ‫ك‬ලಔග‫ٴ‬+ِ੃৘पउऐॊে੟੗஘ਙभ੐ఏ‫ق‬ලಔග‫ّك‬ঽ੘৬पउऐॊ৿೘੟भেඅ‫؞‬ে୘૾யपঢ়घॊঔॽॱজথॢ॑൤఺औचॊ૑ਏऋँॊ

ୖ਻৘ড়धੈ௮दষअে੟ঔॽॱজথॢपି৯ख‫ؚ‬जभ஍ટ৓ऩৰ઱‫؞‬ણ৷্১॑৹ਪর
ِ৘ড়૞ਸ஑ে੟৹ਪّ

੐ఏரभਝ৒ু১Ŕ ৸ে੟ৌ଴भිၨ৓৹ਪमઍಔदऩः

৯‫௴ق‬௄঻‫ك‬भਯऋ੗ः
‫ܒ‬঵঻੻౏ेॉु
‫ઁٴ‬ୠद
‫ٴ‬শ਋৓प
‫ٴ‬਍੼प ৹ਪखअॊ

‫ܒ‬੐ఏரधऩॉअॊে੟म‫ء‬ٌঽ੘৬ಉभৱમद੐ఏரधऔोथःञে੟ٍ

‫ؼ‬ਜ਼ ॶংও ੯ ‫پ‬ਜ਼ ढ़ড७঑ ੯ਜ਼ ३४গक़ढ़ছ‫ؚ‬঑ॼ঑ওॲढ़ ੯


ಉ





‫ق‬৯హયে੟੗஘ਙਅറ‫ك‬୭୆ओधप৘ড়৹ਪभৌ଴ரधऩॊ੐ఏர॑ਝ৒खथःॊ୻

╟৭৒भઅइ্ृুದ॑৥ैऊपघॊञी‫ؚ‬হ୻भถ಍৹ਪृૌுॹ‫ॱش‬भীෲ॑ৰ઱র













␩
‫ڮ‬
ण
भ
ॱ
ॖ
উ
␪



৹ਪਛટभણ৷্ੁ

‫ٴ‬઱ੁਫ਼ୈऋ਌৯৓
౴௔ൃ৉‫ق‬჈ন૊৘ঽே୭୆௬੼৹ਪ໪ਏਾઔ‫ك‬਷ఈ‫ق‬჈ন૊৘෤भ੦মੑ઺‫ك‬ਲ഍क़ॢॖ५ੂఠ ॱথএএभ୨भ
ੂৄ঩ၴुऋ૞ਸदऌॊॎऊॉृघः৹ਪ॑
ಲਢखथःॊ୻

০৏भன஦‫ٴ‬$,पेॊে੟ரभ
௙શଓஃॶ‫ش‬ঝ

KWWSZZZOXSLQHVQHW

୼ઌऊैਜ਼઼ੲਾ॑ഭा਄ॉ
ঽ৿दঐॵউ৲घॊ୻

୼ઌऊै೘੟ர੡॑ঽ৿
ਖ਼શघॊ९ইॺभ୻

ਠ৉दभে੟ॹ‫ॱش‬भල೶ऩ਄੭ऊैॹ‫ॱش‬भઽૐ‫؞‬ଵ৶ऽदभ঳੪৲पणऩऋॊ

ਠ૔मಖ২पୖ਻ऋँॊऋ‫ؚ‬లਟ৓पॹ‫ॱش‬भਦ౅ਙન৳
प૽য়ण૭ચਙऋँॊ‫ك‬╟ऒोैभૼ୒॑ણ৷खथःॊহ୻॑ৌ଴प‫ؚ‬଑োभ੠भੵ୏‫਻ୖؚ‬ಉभถ಍৹ਪ॑ৰ઱র

‫؟پ‬෤भ੦মੑ઺ृে੟੗஘ਙ৉ୠਅറप৘ড়૞ਸ஑ে੟৹ਪभ੶ൗऋँढञঽ੘৬भ੯भ৹ਪ॑ৌ଴

૚ঽ੘৬ऋুർॉखथःॊਠ૾ ‫ܒ‬৉ୠभে੟੗஘ਙभન৳प੥लणऎृॉ্धम‫ء‬‫ق‬৯హયःऌुभਞ଴઎+3‫ك‬৵ᅆ‫؞‬ཨিेॉ੝૗

৘ড়૞ਸ஑ে੟৹ਪभ஍ટ৓ऩৰ઱‫؞‬ણ৷্১‫ٴ‬൤఺ཟ৅ऋ਌৯৓

્ٌपથ৷धઅइैोॊणभૼ୒ٍ
‫ٴ‬५ঐ঍ध৴৿खञ
क़ख़ঈ*,6ॶ‫ش‬ঝ‫؟پ‬ঽ੘৬भ෤भ੦মੑ઺ृে੟੗஘ਙ৉ୠਅറप੐ఏரྼम৹ਪৌ଴धऩॊে੟ர੡भ੶ൗऋँढञৱમಉ੯॑ৌ଴Ŗथउॉ‫੶ؚ‬ஈ঑५ुକऒॉऋठ
‫ܒ‬ৈಖ২द஍૨ेऎॹ‫॑ॱش‬੭ॊपम‫ء‬‫ٴ‬बैः‫؞‬ણ৷ৰଙ Q ␩ে੟भেඅ૾யभཔ඼৹ ে੟भেඅभ৽ফ૗৲भཔ඼ਪ ে੟ঢ়৴भਠ૾ृୖ਻भཔ඼
ൌ૘ரभ৳৸
ৰ൤఺ཟ৅ऋ਌৯৓भ
ਗਟரभੲਾ໮஋
઱୭୆৾ಆषभણ৷
ঽ੘৬ऋ੗ः
૾৘ড়षभਔ௙ཟ৅‫؞‬ཟ᎝ষ৆ੑ઺षभ৘ড়૞ਸ
ய઱ੁभ୸ਛ૾யृ௬੼
઱ੁपણ৷खथःॊঽ੘৬ु૘ਯभ॔থ ‫ٴ‬ৰ઱‫؞‬ણ৷঱भୖ਻ Q ॣষ৆૙৩ಉभૼ୒ৡਂଌ
␗ষ৆૙৩ಉभয৩ਂଌ
ॺ৹ਪभଃ౺‫؞‬੒઴ਂଌऒोैऋ੗ऎभঽ੘৬द
৘ড়भঔॳঋ‫ش‬३ঙথਂଌ
੥৘ড়भয౫ਂଌ
ુৢघॊୖ਻धऩढथःॊ
ટ৘ড়भૼ୒भਂଌ
␪‫پ‬৹ਪਛટभਦ౅ਙभ૿৳

खऊख‫଻ؚ‬શभ੐ఏரभ৭৒৶૓मਂ৥ᐱटढञ

੐ఏரभਝ৒भखऊञमણ৷৯৓पૢगथ
‫ٴ‬୭୆॑ખ಩घॊ੐ఏர
ളਯँॉअॊ
‫੃ٴ‬৘৲ൊ২पૢगञ੐ఏர
‫ٴ‬ମ੺दॎऊॉृघः੐ఏர

ৗૼ୒भ଑ো૭ચਙŕ ে੟ੲਾभ਄੭‫؞‬໮஋पमௌৡऋऊऊढ

╟੔ਤহ୻॑ถ಍৹ਪख‫ؚ‬৯৓पૢगञ৹ਪभৰ઱৬਑‫؞‬லੌाृৰ઱঱भুದ‫؞‬এॖথॺಉ॑ତ৶র
ତ৶ॖও‫ش‬४઱ੁਫ਼ୈऋ਌৯৓
67(383નੳऔोञ੐ఏரਯऊै௬੼ঐॵউ॑੿ਛख‫ؚ‬৳৸঱੎ਏऩ෤৉॑ਜ਼઼तऐथःॊ୻

൤఺ཟ৅ऋ
਌৯৓

ৈ
ਏ
੷
औ
ो
ॊ
ॹ
␗
ॱ
ಖ
২
଩

ৰ઱৬਑

ਠৃ৹ਪृधॉऽधीभ੠प
৾௙঻भ੍ର॑੭ॊ

ঽ੘৬
৾௙঻
৘ড়
ঽ੘৬
৘ড়

ਦ౅ਙँॊॹ‫ॱش‬਄੭भञी
ে੟भ௙શৡभँॊ৉੪132ಉऋরੱधऩॊ

లਟभ67(383ुଳ৙प৘ড়૞ਸभ
ல্॑ੵ୏घॊ
‫؞‬ၴुऋ௙શदऌॊ੐ఏரप଒৒
‫௴؞‬௄ॖঋথॺಉदয౫୘ਛ

৘ড়૞ਸ஑ে੟৹ਪभ॥‫ॹش‬ॕॿ‫૽ॺش‬धऩॊঽ੘৬૿ਊ঻਱ऐभুਬऌभਁ਀‫ق‬+ফ২ଜ৯૪‫ك‬‫ܒ‬੔ਤহ୻भঀक़ঁक़भુથपेॊ਄ੌभ௓ਤ
‫ܒ‬ঽ੘৬ऋৰ੠भে੟भেඅ૾ய॑౷ऽइथ‫੃ؚ‬৘भে੟੗஘ਙभન৳भञीभ਄ੌ॑
ిજऊण੅ਢ৓पৰ઱दऌॊ঺ভभৰਠष

ᄂᆮ঺ௐở২ᘐૅੲऴ‫إ‬ễỄửấ‫ފ‬ẬẴỦ ♫఍㈨ᮏ࣐ࢿࢪ࣓ࣥࢺ◊✲ࢭࣥࢱ࣮ ⥳໬⏕ែ◊✲ᐊ‫׎‬ዮᄂἳὊἽἇὊἥἋỉႇ᥵ỊẮẼỤẦỤ┈Ꮚ ⨾⏤ᕼ
KWWSZZZQLOLPJRMSODEGGJ
KWWSZZZQLOLPJRMSODEEFJPDLOPDJ 7HO㸸 (PDLO㸸QLOU\RNNDVHLWDL#POPOLWJRMS

54



᪥ᮏ⏕ែᏛ఍
᪥ᮏ⏕ែᏛ఍➨  ᅇ඲ᅜ኱఍ㅮ₇せ᪨ࢧ࢖ࢺ㸦㸧| ਏ຺ॺॵউ | ৯ઃ|঩মেଙ৾ভਸ਼66৚৸বপভ (2019ফ3া‫ؚ‬ઋૺ) ൥౰ਏ຺
ESJ66 Abstract঳ಹ൥౰‫ق‬এ५ॱ‫ش‬৅਀‫ ك‬P2-249 ‫ق‬Poster presentation‫ك‬੃৘ୠभ෤৉भ୤‫؞‬ସ‫؞‬ଦ઼धে੟੗஘ਙभঢ়બ ْBٓ
Urban biodiversity in relation to the amount, structure andnetwork of urban green space ْBٓ*இ৕஖૓ൌ‫ق‬ব੕ଢ଼‫؞‬෤৲েଙ‫ك‬, ஹદఊ‫ق‬ব੕ଢ଼‫؞‬෤৲েଙ‫ك‬, ༐୲৳ส‫ق‬ব੕ଢ଼‫؞‬෤৲েଙ‫ك‬, ঱৙ඥஂ‫ق‬લਆ਩য়প‫ك‬*Miyuki Mashiko‫ق‬NILIM‫ك‬, Osamu Moriya‫ق‬NILIM‫ك‬, Satoshi
Funakubo‫ق‬NILIM‫ك‬, Yusuke Ueno‫ق‬Ishikawa Pref. Univ.‫ك‬੃৘যઠऋ਼ੀ৓पੜਸघॊর‫੃ؚ‬৘पउःथुে੟੗஘ਙभન৳ऋୖ
਻धऩढथःॊ‫੃؛‬৘৔भ౴௔৉‫ൃؚ‬৉‫ؚ‬਷ఈ৉ಉभ෤৉म‫੃ؚ‬৘કড়पधढथମ੺ऩঽேधभऴोँःभৃदँॊधधुप‫ؚ‬ে੟भেඅৃਚ
धखथु௼੎ऩ૬৑दँॊ‫؛‬ॎऋবभ੃৘दम‫ؚ‬যઠ੖૘‫؞‬૘৕ৈೡ঺
ভपৌૢखञ੃৘भ॥থঃॡॺ৲भ৿ऌभরद‫ؚ‬ৗञप৅েखञ૬ऌ৉
भ෤৉৲ृใਝਁୱभૐ৺‫؞‬ગౣऩन෤৉૬৑ऋপऌऎ૗ઍघॊ૭ચਙ
ऋँॊऋ‫ؚ‬जभ੠प੃৘भে੟੗஘ਙभન৳प੥लહऎ෤৉भ৳৸‫؞‬൉ল॑௓ਤघॊपम‫ؚ‬नभங২भૠெद‫ؚ‬नअःढञଡୗभ෤৉ऋ‫ؚ‬नभेअपଦ઼औोोयে੟੗஘ਙ৳৸पఞଖख੭ॊऊधःढञੴৄ॑ତ৶
ख‫ؚ‬෤৉ੑ઺पણ৷घॊऒधऋથ஍धઅइैोॊ‫؛‬जऒदমଢ଼஢दम‫ূؚ‬਎੃৔भ੃৘৲भங২भ౮ऩॊ෇೧पउःथ‫ؚ‬෤৉भ୤‫ؚ‬ସ‫ؚ‬ଦ઼ऋে੟੗஘ਙपनभेअप୶஭घॊऊ৥ैऊपघॊञ
ी‫ؚ‬ে੟ரभলਠൊ਱ध୭୆ਏ౤धभঢ়બ॑ীෲखञ‫؛‬ৌ଴৉मূ਎
23ય৔ऊै੗༂৉ୠपऊऐथਜ਼઼घॊ஘‫ر‬ऩૠெ‫ق‬0.1‫ع‬10haਰ঱‫ك‬
भ61ਁୱधख‫ؚ‬ে੟ॹ‫ॱش‬मऒोैਁୱपउःथ2013‫ع‬2014ফप৹ਪखञ೭థ‫ق‬౴௔ਙ‫؞‬਷ఈਙ‫ؚك‬ఄᵷਙᆦདథ‫ॺق‬থ঎థ‫ॳ؞‬ঙक़థ‫؞‬ংॵॱథ‫఺ك‬ल৉঱㡢៺ਙᆦདథभ૚ரभলਠથ૮भ੶ஈ॑৷ःञ‫؛‬୭୆ॹ‫ॱش‬म‫ؚ‬෤৉भ୤पणःथमਁୱ৔भ෤৉એ஋ಉ॑‫ؚ‬ସपणःथम
ਁୱ৔भ೘੟ரਯृঅड़ॺ‫ش‬উ‫ؚ‬१থॡॳগ॔জभથ૮ಉ॑‫ؚ‬ଦ઼पणःथमਁୱఢఈभ঳৒෇೧पோ૔घॊ෤৉भએ஋ृ৴੥ਙ੐ఏகಉ॑৷
ःञ‫؛‬ীෲभ੥ટ‫ؚ‬ীథණपेॊ੗૘भলਠൊ਱भୀःमৄैोञुभभ‫ؚ‬໪ब‫ਁؚ‬ୱ৔भ෤৉भએ஋ऋপऌऎ‫ؚ‬जभଡਛਏಞधखथ੗஘ऩ೘੟ரृ
অड़ॺ‫ش‬উಉऋோ૔ख‫ؚ‬ఢఈभ෤৉धभ৴੥ਙऋৈःਁୱऺन‫ؚ‬ர੗஘ਙऋৈःൊ਱ऋँढञ‫؛‬ম৅਀दम‫ؚ‬ऒोैभীෲ੥ટ॑ງஂघॊधध
ुप‫ؚ‬੥ટ॑౷ऽइञ੃৘෤৉भ৳৸‫؞‬൉ল‫؞‬ଵ৶भ্਱ਙपणःथ૛
ङॊ‫؛‬঩মেଙ৾ভ

55



᪥ᮏ⏕ែᏛ఍
᪥ᮏ⏕ែᏛ఍➨  ᅇ඲ᅜ኱఍ㅮ₇せ᪨ࢧ࢖ࢺ㸦㸧| ਏ຺ॺॵউ | ৯ઃ|঩মেଙ৾ভਸ਼66৚৸বপভ (2019ফ3া‫ؚ‬ઋૺ) ൥౰ਏ຺
ESJ66 Abstract঳ಹ൥౰‫ق‬ઠ୍৅਀‫ ك‬G01-10 ‫ق‬Oral presentation‫ك‬
A Study on the Selection Method of Indicator Species for
Biodiversity Monitoring in Urban Areas*Keita Aragane, Miyuki Mashiko, Satoshi Funakubo‫ق‬NILIM‫ك‬The conservation of biodiversity in urban areas has become
important topics in urban environmental policy, and that
contributes not only to improve urban living environment but
also to enhance of people's awareness of biodiversity. For thispurpose, it is necessary to assess regional ecosystem
continuously by biodiversity monitoring. However, there arefew municipal governments which have implemented
continuous biodiversity monitoring, due to mainly financial
restrictions. Selecting indicator species is considered to be aneffective way to implement continuous biodiversity monitoring
and assess regional ecosystem within budget constraints. In
this study, we surveyed 30 municipal governments which haveconducting biodiversity monitoring in the Tokyo metropolitan
area for clarifying the selection method of indicator species. As
a result, it was revealed that selected indicator species tended
to differ depending on the purpose of the monitoring, species
identification skills of observers, and degree of urbanization. It
was also found that collaboration with diverse stakeholders(such as scientists, engineers, public administrators, andcitizens) is an effective way to select the appropriate indicatorspecies for biodiversity policies promotion.

঩মেଙ৾ভ

56