著者

Kentaro Kazama

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.18, no.2, pp.117-126, 2019 (Released:2019-07-29)

参考文献数

36

---

Breeding seabirds, often nest at high densities and supply large amounts of marine-derived nutrients, such as nitrogen, in their feces into the ecosystems surrounding their breeding colonies. It has been well demonstrated that the nitrogen supplied by seabirds (seabird-N) into terrestrial ecosystems has a strong bottom-up effect on both producers and consumers. The seabird-N can reach into the surrounding marine ecosystems near the colony through multiple pathways including the surface run-off of rainwater or leaching by ground water. However, in marine ecosystems the bottom-up effects of seabird-N have been rarely documented. A few studies using stable isotope analyses have reported that seabird-N enhances the productivity of both phytoplankton and macro algae. There have been more limited studies documenting similar positive effects of seabird-N on marine consumers. Very little is known about spatio-temporal variations in the effects of the seabird-N on marine ecosystems. To understand the ecosystem functions of seabirds in marine nutrient cycling and the bottom-up effects of seabird-N in marine ecosystems, further research is necessary.

著者

Naoki KATAYAMA Hiroshi UCHIDA Yoshinobu KUSUMOTO Tomohiko IIDA

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.21, no.1, pp.93-114, 2022 (Released:2022-01-31)

参考文献数

69

---

Perennial farmlands such as fruit orchards and vineyards often substitute for natural habitats and provide nesting and foraging habitats for birds. Bird use of perennial farmlands has been investigated mainly in Europe and North America, but far less in Asia, which hosts one-third of identified biodiversity hotspots. We aimed to fill this knowledge gap by performing a systematic review of bird studies in fruit orchards and vineyards in Japan. We screened literature written in English or Japanese including both published and non-peer-reviewed (grey material, e.g., books, abstracts of annual meetings, blogs, and unpublished surveys). The review identified 31 bird species, including four Red List species, that nest in orchards and vineyards in Japan. Several studies have provided insights into the habitat quality of fruit orchards, which appears to vary among bird species. Other studies have reported: (1) the effects of orchard management on bird diversity (e.g., positive effects of organic farming and grass cover on bird richness and abundance); and (2) the ecosystem services by birds (e.g., reduction of pest rodents by predatory Ural Owls Strix uralensis). Our review demonstrates the potential importance of fruit orchards and vineyards to bird species that have adapted to human-modified landscapes, although more quantitative studies are needed to investigate the actual breeding performance of birds. We also illustrate the importance of non-English-language literature, including grey literature, to mitigate ecological knowledge gaps in countries where English is not the first language.

著者

仁平 義明

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.44, no.1, pp.21-35, 1995-04-25 (Released:2007-09-28)

参考文献数

21

被引用文献数

5 11

---

1) ハシボソガラスが自動車をクルミ割りに利用する行動について長期的な観察を行なった2) 信号待ちで停車した自動車の車輪の前にクルミを置き,車がひいたクルミを摂食する事例が頻繁に観察された.このことは,車利用行動が偶然なものではなく意図的な行動であることを疑問の余地がな示していた3) 自動車利用によるクルミ割り行動は,多くの変数(クルミの調達法,クルミの特性,クルミのセッティング方法,時刻,場所,他の個体の存在,待ち行動打ち切りの臨界時間,置き直し行動,食行動)から構成されるバリエーションの多い行動であることが確認された4) 自動車利用行動は,上空から投下する方法では割れないクルミを処理するたあの新たな手段として生まれたものであると考えられた

著者

Haruna SAKAMOTO Daisuke AOKI Shingo UEMURA Masaoki TAKAGI

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.22, no.1, pp.45-56, 2023 (Released:2023-01-26)

参考文献数

54

---

Negative relationships between the degree of parental investment and the presence of unrelated offspring in the nest due to extra-pair paternity (EPP) or conspecific brood parasitism (CBP) are predicted in monogamous species. This is because investing in unrelated offspring is costly to individual parents. However, such strategies may be adaptive for one social partner. Because parental investment changes in response to that by the social partner, the predicted relationship needs to be assessed empirically in wild animal populations, with consideration for male and female parental care. Furthermore, both EPP and CBP must be considered simultaneously in such a study. In this study, we tackled the issue using the semi-colonial Eurasian Tree Sparrow Passer montanus, in which both EPP and CBP were predicted to occur. We tested whether there is a negative relationship between the degree of parental care of both males and females and the presence of EPP or CBP, taking into consideration the parental investment of their social partners, using behavioral observations and parentage analyses based on seven microsatellite loci. The results revealed a moderately high frequency of EPP and CBP within a sparrow colony. A negative relationship between parental care by the social male parent and the presence of EPP was suggested, while this was possibly as a result of the increase in parental investment by their female partner. CBP was also inferred to be linked with male parental investment, while females may have compensated for the cost of CBP in their provisioning efforts by egg rejection. High frequencies of occurrence of both EPP and CBP allowed us to shed light on how parental investment is related to the presence of unrelated young in the complex social system of the Eurasian Tree Sparrow.

著者

Eunok Lee Jun Miyazaki Shinya Yoshioka Hang Lee Shoei Sugita

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.11, no.1, pp.59-64, 2012 (Released:2012-07-03)

参考文献数

18

被引用文献数

14

---

We investigated the origin of the iridescent violet-bluish feathers of the adult Jungle Crow, Corvus macrorhynchos, using microscopic and optical techniques. A single layer of melanin granules was found below the surface of the barbules in the feathers of male crows. Although the barbule microstructure was clearly sexually dimorphic, neither the appearance nor the optical measurements were notably different between the sexes, which indicated that the single layer of melanin granules did not contribute to the iridescent color of the feathers. We also found a thin layer, which we refer to as the epicuticle, at the surfaces of the barbules of both male and female feathers, indicating thin-film interference as the most likely cause of the iridescent color. We investigated this possibility by measuring reflection patterns and spectra. Our results suggest that the weak violet-bluish feather color of the feathers of the Jungle Crow is caused by thin-film interface due to the presence of an epicuticle on the feather barbules.

著者

松岡 茂

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.43, no.1, pp.19-28, 1994-07-25 (Released:2007-09-28)

参考文献数

12

被引用文献数

1

---

地上で採食しているヒヨドリに人間が接近して行って,ヒヨドリの群れが飛び立ったときの,人間とヒヨドリの群れとの距離(飛び立ち距離:FLD)と群れサイズ(SIZE)との関係を野外で調査した.ヒヨドリの群れサイズが大きくなるにつれ,飛び立ち距離が大きくなった.回帰式は,FLD=6.9×ln(SIZE)+26.1であった.ヒヨドリの群れサイズの増加に伴い,群れの広がり(RD)も増加した.回帰式は,RD=1.3×ln(SIZE)-1.1であった.しかし,飛び立ち距離の増加は,群れの広がりの増加だけでは説明できなかった.1羽のヒヨドリの飛び立ち距離の分布をもとに,もっとも神経質な個体の飛び立ち距離が群れの飛び立ち距離を決定するという仮定で,シミュレーションを行なったところ,回帰式SFLD=3.6×ln(SIZE)+28.2を得た.これは,実際のヒヨドリの飛び立ち距離の回帰式の傾きとは有意に異なっていた.実際の群れの飛び立ち距離とシミュレーションの結果との違いを神経質な個体の行動から考察を行なった,その結果,神経質な個体は,単独あるいは小数羽の群れに出現する頻度が低いという予想を得た.

著者

Dean Portelli Nicholas Carlile

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.18, no.2, pp.169-175, 2019 (Released:2019-07-29)

参考文献数

41

---

The Lord Howe Woodhen (Hypotaenidia sylvestris) is endemic to Lord Howe Island off the mid-east coast of Australia and came perilously close to extinction as a result of hunting pressure and introduced predators. A recovery program was implemented in the 1970s to reverse the decline of the species through eradicating introduced predators (pigs, cats and goats) and augmenting the population through an in situ captive-breeding program. In 1980, three wild breeding pairs were taken into captivity from Mount Gower. Over the four years of the captive-breeding program, 76 chicks were produced from the original founders and their progeny and an additional four chicks were artificially reared from eggs collected from a wild pair. Almost all woodhens were liberated across four release sites, but only 13% of released birds were resighted and numbers increased at only one of these sites and then declined. A captive-bred female that was released into the lowlands paired with a wild male (which had been temporarily held in captivity) and bred prolifically, leading to rapid population growth in the lowlands. The subpopulation on Mount Gower increased fivefold in the decade following the captive-breeding program, despite the removal of the three breeding pairs (which were released elsewhere) and receiving no augmentation from the captive-breeding program. The woodhen population continues to expand and it is likely the eradication of invasive rodents from Lord Howe Island during 2019 will facilitate further population growth.

著者

黒田 長久

出版者

The Ornithological Society of Japan

雑誌

鳥 (ISSN:00409480)

巻号頁・発行日

vol.20, no.89, pp.125-129, 1971-06-25 (Released:2008-12-24)

---

Type: Possibly male, a live specimen at examination on Oct. 22, 1970. Six years and fivemonths old. Collected on May 4, 1964 as new-born chick by Mr. K. Yonamine on Minamidaito I., Borodino Is. and has been reared and being kept alive by Mr. Masao Oshiro in Naha City, Oki-nawa I.Measurements: Total L. 470mm, Wing Exp. 1050mm, Wing 330mm (Natural), 340mm (Pres-sed), Tarsus 64mm, Culmen 31mm (Entire), 24mm (From cere). For comparison, the measurements in 10_??__??_, 6_??__??_ of japonicus (from Japan) are: Wing (Natural) _??__??_ 348-368 (Av. 354. 5)mm, _??__??_ 363-373 (Av. 367. 6)mm; Tail _??__??_ 187-210 (Av. 195.6)mm, _??__??_ 205-210 (Av. 207.5)mm (Measured by the author).Description: Similar to Bnteo buteo japonicus as a whole, but is generally more reddish, the tectrices and rectrices being almost chestnut color with distinct regular dark bands. The sides of head, supercilliaries and ear-coverts, as well as foreneck at crop region are distinctly tawny buff.The typical japonicus is buffy white in these regions, and wings and tail lack chestnut color(though there is a weak wash of this color on primaries) and with less regular dark bands, the tail being usually uniformly pale greyish brown. However, the flank pattern is of japonicus-type (Cf. Photos). There is no similarly reddish and so distinctly banded example among Japanese specimens preserved in Yamashina Institute, and is also different from larger-sized continental reddish and banded phase.Range: Minamidaito I., Borodino Is. (The first record).Remarks: Having examined only one bird, it is not clear whether its plumage pattern represents whole Minamidaito population. However, it is reasonable that a darker (redder) population has been established on this southern island. It is decidedly smaller in size than japonicus. Its subspecific name is dedicated to Mr. Oshiro who has reared it from chick. The nest was found by Mr. Yonamine with three eggs which soon hatched but a late hatched chick had disappeared when he examined the nest three hours later. The two chicks were taken by him and one of them was given to Mr. Oshiro.

著者

Hideya Wakisaka Munetaka Nakagawa Keiko Wakisaka Masanobu Itoh

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.5, no.1, pp.133-137, 2006 (Released:2006-08-09)

参考文献数

19

被引用文献数

5

著者

時事新報社

出版者

The Ornithological Society of Japan

雑誌

鳥 (ISSN:00409480)

巻号頁・発行日

vol.8, no.36, pp.Plate1, 1933-05-11 (Released:2008-12-24)

著者

Peter M. VAUGHAN Jessie C. BUETTE Barry W. BROOK

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.21, no.1, pp.3-12, 2022 (Released:2022-01-31)

参考文献数

42

---

Understanding the behavioural responses of bird species to their environments is important for effective conservation, especially in captive-management and resource-provisioning programs. Camera traps present a growing opportunity to research bird breeding and foraging behaviour in situ. Remotely triggered cameras are commonly deployed to study mammals and large terrestrial birds. They are rarely used to survey small or arboreal birds due to habitat constraints. However, a wealth of information about small or arboreal birds can be generated opportunistically from camera traps in the course of collecting data on other taxa. Here, we describe and quantify the types of behavioural information that can be so gleaned, based on over 1,700 small-bird images captured as "collateral" during a geographically extensive mammal-focused camera study in Tasmania, Australia in 2018–2020. Postural analysis of images revealed 10 distinct behaviours. Large- and medium-sized terrestrial bird species were most commonly observed (61.6% of behavioural images), but small and arboreal species were also photographed at high rates (18.4% and 29.5% of behavioural images respectively). Investigative activity was the most commonly observed behaviour in small and arboreal species (around half of all images), but feeding, mating and even very rare behaviours like fur plucking, were also captured photographically. This case study reveals the value of opportunistically analysing camera trap images for small or arboreal birds species, especially when they are of conservation interest, even for cases where deliberately targeting them would not be a cost-effective strategy.

著者

鮫島 正道 大塚 閏一

出版者

The Ornithological Society of Japan

雑誌

鳥 (ISSN:00409480)

巻号頁・発行日

vol.33, no.1, pp.29-38, 1984-08-25 (Released:2007-09-28)

参考文献数

16

被引用文献数

1 3

---

18目42科105属147種(亜種を含む)353個体の日本産および外国産の成鳥と推定した鳥類の晒骨標本を作成し,胸椎について胸椎数とnotariumの形成様式を検索した.(1)胸椎は6-12個と変異に富んでいた.椎骨数は同一科内,同一種内でも変異が大きかった.(2)Notariumは9目12科42種103個体の鳥類に存在した.(3)Notarium の存否,それを形成する胸椎の数や位置,胸椎の synsacrum への参加数は胸椎数と同様に同一科内,同一種内においても変異が大きかった.(4)Notarium は飛翔力の弱いキジ目の全種に存在する一方ゴハト科,ハヤブサ科,ツル科そしてフラミンゴ科などにも存在するので notarium の存否を飛翔と短絡的に関係づけることはできないと推察された.

著者

Christoph Randler

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.15, no.1, pp.1-14, 2016 (Released:2016-02-05)

参考文献数

49

被引用文献数

10

---

Birds of a wide range of species show characteristic movements of their tail, often called tail flicking, tail wagging or tail flashing. Tail flicking refers to vertical up-and-down movements of the tail, while tail flashing is defined as a horizontal movement, often including tail spreading. Here, I review proposed functions of such behaviour. Most relate to communication with conspecifics, predators or prey. Tail flashing may induce movement of the bird's prey that makes the prey more vulnerable to capture (‘prey-flushing’). Tail movements may signal to a predator that the signaller has detected it (‘perception advertisement’), or that the signaller is particularly alert or otherwise difficult to catch (‘quality advertisement’). Further, it may warn conspecifics of predators (‘alarm signal’), or it may advertise quality as a mate, signal social status, or aid in flock cohesion. This behaviour may, possibly, though it seems unlikely, represent a cue rather than a signal in that it benefits the receiver, but not the signaller. For each postulated function, I develop predictions stemming from that function, and interpret the available empirical evidence in the context of these predictions. I finish by synthesising our current state of knowledge and by identifying the future empirical studies that would most improve our understanding of this widespread but unjustly neglected avian behaviour.

著者

牛山 克己 天野 達也 藤田 剛 樋口 広芳

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.52, no.2, pp.88-96, 2003 (Released:2007-09-28)

参考文献数

81

被引用文献数

6 6

---

近年,ガン類と農業との軋轢が高まっているが,これらのガン類の中には保全の対象とされている種も多い.行動生態学的研究は,農業被害管理と保全を共通の視点で捉えることができる.そこで本稿は,ガン類の生息地利用に関する行動生態学的研究がいかに農業被害問題へ応用されているかをまとめた.農業被害の発生メカニズムを明らかにする行動生態学的研究によって,状況に応じた管理方策を提言することができ,効率よく農業被害問題に取り組むことができる.それら管理方策には,防除器具の徹底と代替採食地の提供,そして農業活動や人為的撹乱の管理による生息地管理が含まれる.より大きな空間スケールでは,ガン類の生息地選択を理解することで,保全と農業被害を考える上で重要な,極度に集中化したガン類の分散化対策を生物学的根拠に基づいて行うことができると考えられる.これらの行動生態学的知見を統合することにより,ガン類の分布や個体群動態の予測モデルを構築することができる.個体の行動の進化的背景を組み込んだモデルは,環境の変化に対する個体群レベルの反応を予測することができ,農業被害の予防的管理やガン類の保全における有効な手法となり得る.

著者

平野 敏明 小池 勲 塚原 千明

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.53, no.2, pp.98-100, 2004 (Released:2007-09-28)

参考文献数

10

---

We collected a total of 296 pellets of Eastern Marsh Harriers Circus spilonotus from their winter roosts (two sites) in Watarase Marsh, Tochigi Prefecture between January 2002 and late February 2004. Out of these pellets 18 contained a total of 24 pieces of lead shot. Although most of the pellets (14) contained only one piece of shot, two pellets included two and three pieces of shot. Among the prey species found in the pellets along with lead shot, ducks accounted for 55.6%, and doves and crows 11.1%. A significantly higher frequency of lead shot in Marsh Harriers pellets was found in January and February, during the open season for game birds. Although lead poisoning is not yet known to have had any profound effect on the harriers using the study site, care must be taken to protect them from lead poisoning.

著者

Ioannis Kontogeorgos Nikos Kiamos Patricia Montiel-Ruiz Elisavet Georgopoulou Moysis Mylonas Stavros M Xirouchakis

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.18, no.1, pp.95-110, 2019 (Released:2019-01-29)

参考文献数

98

被引用文献数

4

---

The diet composition and dietary patterns of the Long-eared Owl Asio otus were studied in Mediterranean agrosystems in central Crete (Greece) over the winters of 2009–2015. Overall, 2,819 prey items were recovered from 1,207 pellets, belonging to six taxa of mammals, 22 taxa of birds and four taxa of insects. Small mammals were the most common prey species, accounting for 75.8% by frequency and 79.7% by biomass, followed by birds (23.2% and 20.1%); the latter being rather an island component compared to continental regions. The House Mouse Mus musculus was the most important prey species in the owl's diet (56.3%) ahead of the Wood Mouse apodemus sylvaticus (9.51%) and the Black Rat Rattus rattus (7.9%). The species proved to be a significant rodent predator in olive groves and vineyards during winter months, selecting Wood Mouse and young Black Rat more than expected. Long-eared Owl feeding ecology studies could lead to improved land management and agricultural practices in the rural landscapes of the Mediterranean.

著者

Akira SAWADA Tetsuya IWASAKI Chitose INOUE Kana NAKAOKA Takumi NAKANISHI Junpei SAWADA Narumi ASO Syuya NAGAI Haruka ONO Ryota MURAKAMI Masaoki TAKAGI

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.22, no.1, pp.25-34, 2023 (Released:2023-01-26)

参考文献数

42

被引用文献数

1

---

Empirical ornithologists often analyse dispersal distance by histograms separately drawn for categories of individuals (e.g., sexes), and/or by linear models with normal distribution (e.g., ANOVA). However, theoreticians describe dispersal distance by dispersal kernels with various parametric distributions. Therefore, it is a helpful exercise for empiricists to estimate dispersal kernels from field data. As a model case for such an estimation, we analysed dispersal data of the Ryukyu Scops Owls Otus elegans using a Bayesian Weibull regression model. Estimated dispersal kernels showed that males and individuals fledged from late-breeding nests had short natal dispersal distances and that no factors affected breeding dispersal significantly.

著者

村上 正志

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.50, no.3, pp.115-124, 2001-08-31 (Released:2007-09-28)

参考文献数

49

被引用文献数

3 3

---

河畔林(riparian forest)は野生生物の生育•生息環境として非常に重要である.鳥類についても数多くの研究が河畔林における高い生息密度や種多様度を示しているが,その高い多様性を説明する要因としては,(1) 河畔林の複雑な植生構造,(2)河川-河畔林-後背林という景観の多様性,(3)コリドーとしての機能(4) 境界における生物間相互作用の複雑さ,(5) 後背林からの栄養塩の供給による河畔林における生産性の高さ,(6)河川からのエネルギーの移流があげられる.とくに近年は,水域と陸域の境界面としての河畔林の機能が注目されている.しかし,わが国においては鳥類の群集研究,とくに景観生態学的な視点を組み入れた研究は極あて少ない.鳥類の多様性保全における河畔林さらには景観の多様性の機能解明に向け,今後このような研究が必要とされるであろう.

著者

Alima DORZHIEVA Makoto NAKATA Keisuke TAKANO Youki FUJIHIKO Yasuo ITO Kiyoshi AKAHARA Katsuyoshi TACHIKAWA Yasuko ICHIMURA Yaeko FURUKAWA Hiroshi SATO Mikiko FUJISAWA Mika OKAMOTO Takehiko SHIMIZU

出版者

The Ornithological Society of Japan

雑誌

ORNITHOLOGICAL SCIENCE (ISSN:13470558)

巻号頁・発行日

vol.19, no.1, pp.41-53, 2020 (Released:2020-01-30)

参考文献数

45

被引用文献数

2

---

Changes in the timing of bird migration in spring and autumn in a coastal forest near the city of Niigata, central Honshu, Japan, were analyzed based on 27 years of bird-banding records. Half of the bird species studied, including all migratory types except residents, arrived or departed significantly earlier in spring due to an increase in spring temperatures. The rate of change we observed in spring migration timing due to changes in temperature was identical to or slightly greater than those reported in studies from other countries. The spring arrival of the Narcissus Flycatcher Ficedula narcissina and the Japanese Thrush Turdus cardis, both long-distance summer migrants to the nearby mountains, became earlier (advanced), however, for reasons that remained unclear. Median capture date in autumn was significantly associated with year for five species. Of these, the median capture date of the Japanese White-eye Zosterops japonicus, a resident and wandering bird, and the Black-faced Bunting Emberiza spodocephala, a wandering bird, advanced annually, while for the Japanese Robin Luscinia akahige and two other species (all long-distance migrants), it was delayed. We hypothesize that forest succession from a simple pine forest to a mixed forest with well-developed sub-canopy and shrub layers may have strongly influenced the Japanese White-eye and the Black-faced Bunting due to changes in population structure in the study area, resulting in an earlier median autumn capture date. Forest succession may also have influenced the Japanese Robin's food resources, enabling it to stay longer in the study area and resulting in a delay in autumn departure date. Thus, changes in bird migration timing differ according to different environmental factors in spring and autumn.

著者

濱尾 章二

出版者

The Ornithological Society of Japan

雑誌

日本鳥学会誌 (ISSN:0913400X)

巻号頁・発行日

vol.40, no.2, pp.51-65, 1992-02-25 (Released:2007-09-28)

参考文献数

35

被引用文献数

16 14

---

1) 1990,91年の繁殖期に新潟県妙高高原において,190個体(うち成鳥80個体)のウグイスを個体識別して,婚姻形態の解明を目的とした調査を行った. 2) 1991年,118haのセンサス調査区では,踏査の際10-14個体(x=11.7,n=9)のなわばり雄が確認された.同調査区ではシーズン全体で35個体のなわばり雄が確認された,なわばり雄の交代は頻繁に起こっており,なわばりは短期間しか維持されなかった. 3) 他のなわばりにさえずることなく侵入する雄が見られた.詳細に調査した1なわばりでは,20例の侵入が確認され,このうち15例が放浪雄によるものであった. 4) 雄のなわばり内で同時期に複数の巣が発見されることがあり,精密に調査した1なわばりでは,1シーズンに6ないし7雌によって7巣が営まれた. 5) 造巣,抱卵,育雛はすべて雌のみによって行われ,捕食者に対するモビング,巣外育雛を含め,雄は一切の子の世話を行わなかった. 6) 捕食によるものと推定される繁殖失敗が多かった,第2繁殖を含めて,雌は再繁殖の際に雄のなわばりを変える傾向があった. 7) 詳細に調査した1なわばりでは21個体の雌が確認され,雄にとってどの時期でも配偶可能な雌が供給されやすい環境であることが示された. 8) 営巣雌の行動範囲は雄のなわばりに比べてかなり狭く,結果的に雌がなわばり外で行動することは少ないものと考えられた.また,同一なわばりに営巣した雌間の行動圏は重複しており,排他的な行動は見られなかった. 9) なわばり雄と営巣雌間には,求愛以外に接点が観察されなかった.雄のさえずり頻度にも営巣雌のステージと対応した変化は見られず,雌に対する雄の追尾行動も観察されなかった. 10) これらのことから,ウグイスは番い関係がきわめて希薄な一夫多妻の婚姻形態をもつものと考えられた.