Promoting the use of renewable energy and conserving biodiversity are conflicting issues that need addressing. While the development of offshore wind facilities/turbines is accelerating, many seabirds have been exposed to collisions with wind turbines. We must identify high collision areas and avoid the construction of wind turbines in these spaces to reduce these conflicts. One solution is to develop useful finer scale sensitivity maps. In this study, we created a fine-scale map of collision risk by spatial modelling using information from bird flights at sea and explored the relative importance of each geographic variable relevant to the risk. Between 2016 and 2019, we collected 3D-location data from 117 black-tailed gulls (Larus crassirostris) of three colonies in two areas and 21 slaty-backed gulls (L. schistisagus) of four colonies in one area of northern Hokkaido, Japan. The spatial models that explain the occurrence of M-zone flight, which is the flight within the heights of high collision risk (20–140 m height), were constructed at a 1 km mesh using a random forest algorithm, a machine-learning tool. The model satisfactory predicted the spatial distribution of M-zone flights using geographic variables and species (correlation coefficient: 0.57–0.94), although data had some degrees of variation between species, years, colonies, and areas. Our model can be applied to other regions, as long as we have general topological information and the locations of colonies and harbors. The distance to the breeding colony and the nearest harbors were important, and the collision risk was 6–7 times higher within 15 km from the colonies and 5 km from harbors. Black-tailed gulls used different sites for foraging and commuting between years, whereas slaty-backed gulls used relatively consistent sites. These variations between species and among years suggest that collecting bird data over multiple years is necessary and effective for creating a generally applicable sensitivity map.

Areas at which seabirds forage intensively can be discriminated by tracking the individuals' at-sea movements. However, such tracking data may not accurately reflect the birds' exact foraging locations. In addition to tracking data, gathering information on the dynamic body acceleration of individual birds may refine inferences on their foraging activity. Our aim was to classify the foraging behaviors of surface-feeding seabirds using data on their body acceleration and use this signal to discriminate areas where they forage intensively. Accordingly, we recorded the foraging movements and body acceleration data from seven and ten black-tailed gulls Larus crassirostris in 2017 and 2018, respectively, using GPS loggers and accelerometers. By referring to video footage of flying and foraging individuals, we were able to classify flying (flapping flight, gliding and hovering), foraging (surface plunging, hop plunging and swimming) and maintenance (drifting, preening, etc.) behaviors using the speed, body angle and cycle and amplitude of body acceleration of the birds. Foraging areas determined from acceleration data corresponded roughly with sections of low speed and area-restricted searching (ARS) identified from the GPS tracks. However, this study suggests that the occurrence of foraging behaviors may be overestimated based on low-speed trip sections, because birds may exhibit long periods of reduced movement devoted to maintenance. Opposite, the ARS-based approach may underestimate foraging behaviors since birds can forage without conducting an ARS. Therefore, our results show that the combined use of accelerometers and GPS tracking helps to adequately determine the important foraging areas of black-tailed gulls. Our approach may contribute to better discriminate ecologically or biologically significant areas in marine environments.

The strongest earthquake of 2011 hit eastern Japan and triggered the Tohoku tsunami that severely affected the northeastern coast of Japan. The coastal soil ecology and seabird colonies were significantly changed by the tsunami. We investigated the physicochemical dynamics of ornithogenic nitrogen derived from the uric acid in seabird feces in soil splashed or flooded by the tsunami. The analyses suggested that soil leaching in areas flooded by the tsunami led to a change in ornithogenic nitrogen, particularly suppression of nitrification. In the present study, we performed next-generation sequencing (NGS) and statistical analyses to compare the bacterial community structures of ornithogenic soil in areas splashed or flooded by the tsunami, and identified how the suppression of nitrification affected the microbes in ornithogenic soils. The statistical analyses based on NGS revealed that the dynamics of NO3−-N in the splashed soils was affected by the structure of the microbial community involved in denitrification and/or dissimilatory nitrate reduction to ammonium, and that the dynamics of NH4+-N in the flooded soils was not affected by nitrifying bacteria. The results of the statistical analysis also indicated that the differences in microbial community composition detected between splashed and flooded soils affected their nitrogen cycling. Our results provide insights into the microbial effect of nitrogen cycling in soil environments affected by the tsunami.

動物の個性についての研究は2000年代に入ってから盛んに行われている。しかしながら、集団生活する動物種において、個性が集団中の他個体にどのように影響し集団のパフォーマンス（採餌成功、探索行動の活発さ、対捕食者防衛の成否など）を変化させるのかはよくわかっていない。本稿では、はじめに、集団繁殖するウミネコの捕食者に対する攻撃性が、隣接個体の繁殖成績に及ぼす影響についての実証研究を紹介する。集団繁殖するウミネコは卵捕食者であるハシブトガラスに対して防衛行動をとるが、その防衛強度の個体変異は大きく、全体の3割ほどのオスのみがカラスに対して積極的に防衛し（攻撃的個体）、残りの個体はほとんど防衛しなかった（非攻撃的個体）。抱卵期において、攻撃的個体は積極的な対捕食者防衛によって自身の巣だけでなく隣接する巣の卵捕食率も低下させた。抱卵期においてカラスに対して攻撃的であった個体は、育雛期にはヒナ殺しのために縄張りに侵入してくる同種個体に対しても攻撃的な反応を見せた。対捕食者防衛と同様に、攻撃的個体は積極的な防衛により自身のヒナだけでなく隣接個体のヒナの生残率も上昇させた。ウミネコでは、集団内における攻撃的個体と非攻撃的個体の比率によって集団の平均的な繁殖成功度が変化することが示唆された。続いて、こうした集団におけるメンバーの個性の比率が集団レベルのパフォーマンスに及ぼす影響についての実証的な研究事例をレビューする。いくつかの研究は、集団レベルのパフォーマンスは、集団メンバーの個性の比率だけではなく、キーストーン個体と呼ばれる特定の個性を有する個体の存否によっても変化することを示した。これら個性の比率やキーストーン個体の存在は、集団あたりの採食成功率、交尾機会、あるいは微生物感染率を変化させ、個体群動態にも影響を及ぼすことが示唆されている。一方、集団メンバーの個性の比率がどのように維持または変化していくのかはほとんど明らかにされていない。集団に加入した個体の個性は、集団の特性に応じて可塑的に変化する可能性もある。集団と個性との相互関連性の理解のためには、今後さらなる実証的知見の蓄積が必要である。

<p>洋上風力発電は陸上風力発電よりも極めて大きな発電量を持つことから、近年気候変動問題の緩和策として最も有力視されている再生可能エネルギーのひとつである。その一方で、風車への海鳥の衝突等、野生動物への影響も懸念されている。このため、海鳥の生息に配慮した風力発電事業計画のための実用的なセンシティビティマップが求められるが、多くの国で作成されていない。本研究は、海鳥類への影響を最小限にとどめることを目的に、オオセグロカモメ Larus schistisagusをケーススタディとし、本種の生息場選択に関わる要因を明らかにし、センシティビティマップを作成した。 2018年 6－8月に、北海道道東地方に生息するオオセグロカモメ 6個体に GPSロガーを装着し 5分間隔で利用場所を特定した。オオセグロカモメの利用頻度は海水面温度、クロロフィル a、および営巣地からの距離が関係しており、海水面温度やクロロフィル aの上昇に伴い増加し、営巣地からの距離に応じて減少した。しかし、営巣地からの距離が 25 kmを越えた辺りからは横ばいとなった。これらの結果を用いてセンシティビティマップを作成したところ、営巣地に近接した海域だけでなく、遠方であっても潜在的に餌資源量が多い海域であれば、本種が風車に衝突する可能性が高くなることが示唆された。国内での洋上風力発電事業が計画されつつある今日では、本研究で示された手順で緊急にセンシティビティマップを作成し、事前の開発地選択に活用する必要がある。</p>

Breeding population abundance such as colony size of seabirds is not generally considered to be particularly sensitive to the annual dynamics of the food conditions because of the long life-span and high adult survival rate. However, in seabird species in which adults decide to breed or not depending on the food conditions, population abundance can respond sensitively to the annual variation in the food conditions. Here, we examine the effects of the regional annual stock abundance of Japanese Sand Lance Ammodytes personatus, and their local temporal availability during the egg-laying period on the size of a Black-tailed Gull Larus crassirostris and Slaty-backed Gull L. schistisagus, breeding colony over 12 years on Rishiri Island, northern Japan. The total number of nests of both gull species increased significantly with the regional annual stock abundance, but not with the local temporal availability of the sand lance. The number of Black-tailed Gull nests without eggs was significantly higher in the year with lower local temporal availability indicating that more Black-tailed Gull parents gave up egg-laying after nest building. Colony size in these species can be a useful indicator reflecting local food conditions.

Large amounts of marine-derived nitrogen are carried ashore by seabirds in their feces (ornithogenic N). Various topological, meteorological; and environmental factors can affect microbial transformation of ornithogenic N altering the physical and biochemical conditions of the soils. Tsunami may be a factor affecting ornithgenic soil N dynamics leading to changes in soil conditions. We examined the effects of the tsunami triggered by the 11 March 2011 earthquake off the East Coast of Honshu. Japan, on ornithogenic soil N in the Black-tailed Gull Larus crassirostris breeding colony on Kabushima (Kabu Island) four months after the disaster. There were no differences in the total N content in soils between tsunami splashed (upper half of the island) and flooded areas (lower half), and the visual topographv was comparable to that reported before the tsunami. It seems that the tsunami may not have extensively removed accumulated omitliogenic N in the soils, nor did it induce deposition of organic matter derived from marine sediments. However, delta N-15 values of soil N were lower in the area flooded by the tsunami than in the splashed area, suggesting the possibility that the tsunami caused leaching of ornithogenic N from the soil. Soils flooded by the tsunami contained higher levels of marine salts than those from the splashed area. N isotopic differences between NH4- and NO3-N were smaller in the flooded soils than in the splashed area. This indicates that nitrification of ornithogenic soil N is suppressed in the flooded area because of the remarkable increase in the salt concentration of the soil.

鳥類が担う多様な生態系機能の大部分は，生態系サービスとして人間に利益をもたらす．そのうち供給サービスや文化サービスは古くから人間に認知されてきたが，基盤サービスや調整サービスの認知度は低く，その価値評価も不十分である．鳥類は捕食，移動，および排泄を通じて，種子散布・花粉媒介，餌生物の個体数抑制，死体の分解・除去，および栄養塩類の循環などの多様な生態系機能を担う．これらは，有用植物の生産性向上，有害生物の防除，生息環境の創成・維持などの利益を人間にもたらす．近年ではこれら生態系サービスの価値を経済的に評価する試みがなされているが，その実例は少ない．主に農耕地生態系において古くから鳥類の生態系サービスを享受してきた日本においては，その理解と価値評価がとくに必要とされる．

ウトウCerorhinca monocerata雛にイカナゴAmmodytes personatusとナンキョクオキアミEuphausia superbaを給餌し，その消化率と成長を調べた．イカナゴについては，雛に1日あたり湿重量で79.4&plusmn;3.1 gwet/d（平均&plusmn;標準偏差）与え，497.2&plusmn;14.9 kJのエネルギー価，4.3&plusmn;0.2 gの脂質，12.3&plusmn;0.5 gのタンパク質を含んでいた．オキアミについては，雛に1日あたり湿重量で129.3&plusmn;2.7 gwet/dを与え，746.8&plusmn;15.5 kJのエネルギー価，3.1&plusmn;0.1 gの脂質，23.3&plusmn;0.5 gのタンパク質を含んでいた．窒素補正で修正した消化率，見かけの代謝エネルギー率はイカナゴを与えた雛で82.8&plusmn;0.5％で，オキアミを与えた雛の76.6&plusmn;0.6％より有意に高かった．実験期間中のイカナゴ雛とオキアミ雛の成長速度は11.0&plusmn;4.7（g/d, n＝12）と9.7&plusmn;2.7（g/d, n＝14）であった．オキアミを与えられた雛の体重増加は，日齢の効果を考慮すると，イカナゴを与えられた雛の値よりも有意に低かった．イカナゴに比べ脂質の少ないオキアミは雛の成長には不適当な餌かもしれない．

東海地方のカワウPhalacrocorax carboの餌組成に基づき，カワウの餌である魚類とエビ類の栄養組成とエネルギー価を測定した。2005年から2012年の間に，カワウの19の餌種を，コロニーで吐き戻しを拾ったり，コロニー付近の海や川で釣りをしたり，魚屋から購入したりすることで集めた。粗脂肪はアメリカザリガニProcambarus clarkiiの0.6%からマアナゴConger myriasterの38.2%，エネルギー価はアメリカザリガニの12.43 kJ/gからマアナゴの27.79 kJ/gと，餌種間の差が大きかった。

プランクトン食ウミスズメ科鳥類では，繁殖前に低い栄養段階の餌（カイアシ類）を食べたメスが大きな卵を産む．北海道天売島のウトウ Cerorhinca monocerata は魚食性であるが，春にはオキアミも食べる．卵容積に影響する要因を調べるため，2010，2011，2012年に抱卵中のオス・メスを捕獲し，その体サイズと余剰栄養指標，胸の羽毛と血球の窒素安定同位体比（&delta;¹⁵N，栄養段階の指標）を調べた．加えて，いつの時期に食べた餌が卵形成に利用されるか推定するため，2011年と2012年には別の巣から産卵後1日以内の卵を採取し，卵黄，卵白および卵膜の&delta;¹⁵Nと&delta;¹³C（炭素安定同位体比）と抱卵中のメス親の胸の羽毛，血球および血漿のこれらの値との関係を調べた．また，産卵・抱卵期に胃洗浄法によって他の個体から胃内容物を採取し，食べていた餌種を直接調べた．余剰栄養指標・体サイズの大きいメス，またつがい相手の体サイズが大きいメスほど大きな卵を産んでいた．産卵～抱卵時期には栄養段階の低い餌（オキアミ）と高い餌（魚）を食べていたが，造卵期の栄養段階を反映する血球の&delta;¹⁵Nの個体変異は卵容積指数に影響しなかった．また換羽期の栄養段階を反映する胸の羽毛の&delta;¹⁵Nも卵容積指数と関係なかった．卵黄，卵白および卵膜の&delta;¹⁵N，&delta;¹³Cは，換羽期と産卵前のいずれの時期に食べた餌の栄養段階とも関係が認められなかった．

Long-lived animals sometimes skip one or more breeding seasons; however, little is known about their movements and activities during such sabbatical' periods. Here we present novel data on year-round movements and activities of two male black-tailed gulls Larus crassirostris during a sabbatical year. We compare the data with those in a year when they bred and with those of two other breeding males. The year-round migration routes of two sabbatical males were consistent with those of the breeding males: they returned to the breeding area but did not visit the colony in the sabbatical year. They landed more frequently on water (a potential index of foraging effort) during the non-breeding autumn and winter prior to the sabbatical year than before breeding. Sabbatical gulls may forage more intensively to recover body condition immediately after breeding.

カワネズミChimarrogale platycephalaの捕獲率に影響する環境要因を調べるため，2011年5月から12月まで愛知県豊田市矢作川水系神越川の3つの支流で捕獲調査を行った．カワネズミの捕獲率は河川の合流地点，または国土地理院発行2万5千分の1地形図に未記載の微小河川で高く，また150 mm/日の降雨の後3日間に高い傾向があった．小規模な工事残土の流入は捕獲率に影響していなかった．<br>

海鳥の繁殖期の食性は，繁殖成績の年変動や地域差を生み出す要因の一つである．カワウPhalacrocorax carboの繁殖成績は繁殖地や年ごとに大きく異なることが知られているが，本種の繁殖期の食性の地域差や年差はあまり知られていない．本研究では中部地域の5つのカワウのコロニーにおいて，2009-2011年の育雛期の食性を吐き戻しの収集により調査した．カワウの食性は年や場所によって大きく異なった．沿岸域のコロニーでは多くの年でボラMugil cephalus cephalusやコノシロKonosirus punctatusの出現割合が70％以上を占めた．内陸域のコロニーでは，沿岸域とは異なり，いずれの年においても多様な餌種が出現した．沿岸・内陸いずれのコロニーにおいても，魚類の出現割合が低い年には代わりにアメリカザリガニProcambarus clarkiiやテナガエビMacrobrachium nipponenseが出現した．

屋外で人工飼育されたカワウPhalacrocorax carbo hanedae亜成鳥の摂餌量と体重を117日間毎日測定した。外気温が上昇するにつれ，飽食給餌された5個体のカワウの体重当たりの摂餌量は減少したが，体重増加率（体重に対する体重増加量の割合）は減少しなかった。外気温が上昇すると，おそらく体温調節にかかるエネルギーコストが減少するため，カワウのエネルギー消費量が低下すると考えられた。

Terrestrial ecosystems near breeding/roosting colonies of piscivorous seabirds can receive a large amount of marine-derived N in the form of bird feces. It has been well demonstrated that N input from seabirds strongly affects plant communities in forests or coastal grasslands. The effects of nutrient input on plant communities in agricultural ecosystems near seabird colonies, however, have rarely been evaluated. This relationship was examined in rice-paddy fields irrigated by a pond system located near a colony of the Great Cormorant Phalacrocorax carbo in Aichi, central Japan. In the present study, spatial variations in N content (N %) and N stable isotope composition (δ15N) of soils and wild grass species together with the growth height of plants in paddy fields in early spring (fallow period) were examined. Soils had a higher N % and δ15N values in fields associated with an irrigation pond that had N input from cormorants. The δ15N values tended to be higher around the inlet of irrigation waters, relative to the outlet. These results indicate that cormorant-derived N was input into the paddy fields via the irrigation systems. Plants growing in soil with higher δ15N had higher δ15N in the above-ground part of the plants and had luxurious growth. A positive correlation in plant height and δ15N of NO3-N was observed in soil plough horizons. © 2012 Elsevier Ltd.

To understand the adaptive significance of colonial breeding, evaluating the costs and benefits that colonial breeding provides to individuals is necessary. To study some of these costs and benefits of colonial breeding, over 24,000 nest-hour observations of kleptoparasitism (stealing of food being fed to young), intraspecific attacks on and killing of chicks; and chick adoption were conducted in colonial breeding Black-tailed Gulls (Larus crassirostris) during two breeding seasons. Although kleptoparasitism was rarely observed (under 0.001 events/nest/observational hour), the occurrence of chick-attacks was 5-10 times higher (0.005-0.01 events/nest/observational hour) than that of kleptoparasitism, with over 10% of the attacks resulting in the death or disappearance of chicks. More than 60% of all attacks on chicks were by failed breeders and non-breeding adult floaters. The survival of attacked chicks reached 98-100% if they escaped into other nests and were accepted by "foster" adults, or if they were defended by non-parental,adults. Chick adoption and non-parental defense were more likely to be observed among breeding neighbors (52-60% of chick adoptions and almost all examples of non-parental defense) than among non-neighbors. An increased chick survival rate, resulting from nesting in close to proximity to conspecific neighbors, was considered as a factor promoting colonial breeding among the Laridae. Received 20 January 2012, accepted 5 August 2012.

Carbon and nitrogen stable-isotope ratios were measured in the egg yolks of four species of seabirds in Teuri Island and Rishiri Island, Japan. Delta N-15 of the yolks of Rhinoceros Auklets Cerorhinca monocerata (11.2-12.3 parts per thousand) and Black-tailed Gulls Larus crassirostris (11.3-12.5 parts per thousand) were lower than those of Slaty-backed Gulls Larus schistisagus (13.4-14.2%0) and Japanese Cormorants Phalacrocorax capillatus (14.0-16.2 parts per thousand); suggesting that the former two species foraged mainly on low trophic level small fishes and sometimes on krill, while the latter two species fed on higher trophic level prey and larger fishes.

Individual behaviors of animals do not evolve separately; they do so in association with other behaviors caused by single shared genetic or physiological constraints and/or favored by selection. Thus, measuring behavioral syndromes-suites of correlated behaviors across different contexts-leads to a better understanding of the adaptive significance of variations in behaviors. However, relatively few studies have examined behavioral syndromes in wild animal populations in changing environments. We investigated a potential behavioral syndrome across antipredator nest defense, territorial defense, chick provisioning, and mating behaviors of male Black-tailed Gulls Larus crassirostris in two successive years under different conspecific territorial intrusion risks and food conditions. Males that presented high levels of antipredator nest defense (aggressive antipredator defenders) against a crow decoy (crows are egg predators) defended their territories against conspecific intruders more frequently than did other males (nonaggressive antipredator defenders), independent of the risk of intrusion. Aggressive antipredator defenders also fed their chicks more frequently than nonaggressive males, but only in a year of low food availability. Taken together, this indicates that males show consistent aggressiveness regardless of breeding context (antipredator and territorial defense), but can regulate food provisioning according to food availability.

In some bird species, the survival of chicks hatching later in the season is lower than those hatched earlier due to increased risk of predation and a seasonal decline in feeding conditions. To reduce these risks, it might be advantageous for late-hatched chicks to grow faster and hence fledge at younger age. In this experimental study, the growth rates of early- and late-hatched Rhinoceros Auklet Cerorhinca monocerata chicks were compared under average and poor food supplies in captivity. Controlling for potentially confounding effects of chick mass at 10 days old, chick age and nest-chamber temperature, late-hatched chicks had higher wing growth rate than early-hatched chicks before attaining the minimum wing length required for fledgling under both average and poor food supplies. After attaining the minimum wing length, however, late-hatched chicks had a lower fledging mass, indicating a potential cost that could diminish the early advantage of fast wing growth.

近年、陸上の建設適地の不足や電力供給の安定性から、大規模な洋上風力発電施設(洋上風発)が世界各地に建設されている。洋上風発は、建設や運用に関して多くの経済的利点を保有している一方で、海洋生物へ様々な影響をおよぼす。洋上風発建設前の探査や掘削により発生する騒音は、魚類や海棲哺乳類の音声コミュニケーションを阻害する。洋上風車の設置は、海洋生物の生息場所を減少させるばかりでなく、局所的な海洋環境を変化させることを通してさまざまな海洋生物の生残や繁殖に影響をもたらす可能性がある。また、洋上の風車と鳥類が衝突する事故は多数確認されている。風車との衝突を避けるために、多くの鳥類が採餌や渡りの際に風車を避けて飛翔する。この風車回避行動は、鳥類の飛翔距離の増加を招き、その分、飛翔エネルギーコストが上昇すると考えられている。今後、より多くの海域や分類群を対象とした長期的な影響評価が必要である。洋上風発が海洋生物におよぼす影響を軽減するためには、多くの鳥類や海棲哺乳類が利用する渡り・回遊ルートや採餌域を避けた建設地の選定、騒音の発生を抑えた工法、渡り・回遊や繁殖の時期や時間帯に配慮した運転などが求められている。

The physiological state of parent birds combined with the value of their clutch may affect the intensity of their nest defense. In colonially breeding birds, nest-defense intensity may also be affected by the behavior of neighbors. We investigated individual variation in the nest-defense intensity among colonial Black-tailed Gulls (Larus crassirostris Vieillot, 1818) over 2 years. Only 30%-40% of males attacked a decoy of an egg predator (Large-billed Crow (Corvus macrorhynchos Wagler, 1827)), and the other males and females rarely attacked. Males attacking the decoy had higher levels of plasma testosterone than males that did not attack. Each male&apos;s, but not female&apos;s, nest-defense intensity was consistent throughout the incubation period and also across years. The intensity was not related to egg-laying date, clutch size, or age of offspring. The intensity was likely to be higher when individuals had one or more neighbors, representing higher nest-defense intensity in the year where gulls had larger number of adjacent neighboring nests (5.23 nests), but this trend was not observed in the year where they had smaller number of the neighboring nests (3.73 nests). Thus, in addition to testosterone levels, behavior of neighbors also influences the nest-defense intensity.

Seabirds and large fishes are important top predators in marine ecosystems, but few studies have explored the potential for competition between these groups. This study investigates the relationship between an observed biennial change of pink salmon (Oncorhynchus gorbuscha) biomass in the central Bering Sea (23 times greater in odd-numbered than in even-numbered years) and the body condition and diet of the short-tailed shearwater (Puffinus tenuirostris) that spends the post-breeding season there. Samples were collected with research gill nets over seven summers. Both species feed on krill, small fishes and squid. Although the mean pink salmon catch per unit effort (in mass) over the study region was not related significantly with shearwater&apos;s stomach content mass or prey composition, the pink salmon biomass showed a negative and significant relationship with the shearwater&apos;s body mass and liver mass (proxies of energy reserve). We interpret these results as evidence that fishes can negatively affect mean prey intake of seabirds if they feed on a shared prey in the pelagic ecosystem.

Testosterone affects male sexual-, aggressive-, and parental-behaviors in bird species. To understand the breadth of the proximate contribution of testosterone to breeding behaviors in male Black-tailed Gulls Larus crassirostris, sexual behaviors, aggressive behaviors against egg-predators and conspecifics, and chick-provisioning behavior of five testosterone-implanted males (T-males) were observed and compared with those of three control males (placebo-implanted; C-males). T-males showed significantly higher levels of courtship and copulation behaviors than C-males. The levels of aggressiveness against egg-predators and against conspecifics, and the rate of feeding of chicks did not differ between T- and C-males. These results suggest that sexual and mating behaviors in male Black-tailed Gulls may be affected by testosterone, while aggressive- and feeding-behaviors are affected by certain ecological factors, such as individual age, or a necessity for high levels of feeding by males, rather than by testosterone.

Mother birds can enhance growth and/or survival of chicks by supplying energetic and hormonal resources to the egg yolk (i.e. maternal effect). In several bird species, mothers supply higher level of testosterone to the eggs laid later within the clutch and enhance the growth of the chick to compensate for the disadvantage of the later hatching. As same as this within-clutch mechanism, mothers breeding later in the season can be expected to supply higher level of testosterone to the clutch. However, among-clutch seasonal variation in yolk testosterone levels has been rarely described. Here, we investigated among-clutch seasonal variation in the yolk testosterone level in Black-tailed Gulls Larus crassirostris, as well as within-clutch variation. Mean yolk testosterone level of eggs laid later within the clutch ("b-eggs") was significantly higher than that of eggs laid earlier ("a-eggs"). The yolk testosterone levels of both a- and b-eggs of later breeders were significantly higher than those of earlier ones, while this trend was not observed in mean egg mass. Our results indicate that mothers establishing the clutch later in the season would invest more maternal testosterone into the clutch.

海洋における人間活動の影響によって，海洋生態系の重要な構成員である海鳥は現在その個体数を大きく減少させている．これら海鳥の保全のためには，その個体数や繁殖成績がどのような要因の影響を受けて変動しているのかを詳細に理解する必要があり，その繁殖や個体数モニタリングは必要不可欠である．本稿では，簡便な海鳥モニタリング調査である海岸漂着海鳥調査および船舶からの洋上分布調査（海上センサス）の手法を紹介し，その意義について解説する．海岸漂着海鳥調査は，一定距離の海岸を歩き，海岸に打ち上げられた海鳥の死体などを記録するという，簡便で市民が容易に参加できるモニタリング手法である．海上センサスは，調査船，商船やフェリーを用いて海鳥の洋上分布や行動についての調査するモニタリング手法である．特にフェリーによる海上センサスは，双眼鏡などがあれば誰でも実施可能な調査であるため，海岸漂着海鳥調査と同様に専門家でない市民でも実施可能なモニタリング手法の一つと言える．現在，海鳥がとくに頻繁に利用する海域（海鳥重要生息地）を特定する試みが世界中で進んでいる．海上センサスは，この海鳥重要生息地の特定において重要な情報を提供する．継続的な海岸漂着海鳥調査は，特定された海鳥の重要生息地において油汚染や海鳥の混獲などが発生していないかを継続的に監視する役割を担う．海岸漂着海鳥調査や海上センサスなどの市民参加型の調査が広く普及し，各地で定期的に，継続的に実施されることが期待される．

Often in colonial seabirds, all colony members are believed to defend against nest predators and experience equal nest predation risk. However, the variation of defense behavior among members and its reproductive consequences are largely unknown. We investigated (1) individual variation in the nest defense of breeding Black-tailed Gulls Larus crassirostris against a natural egg predator, the Jungle Crow Corvus macrorhynchos and (2) how this behavioral variation affects an individual&apos;s own nest predation risk and that of their neighbors. Results were compared between 2 years where crow attack levels were manipulated to average 5 and 22 times normal rates ("low" and "high" predation risk years, respectively) by the placement of varying numbers of artificial nests containing unguarded eggs at the perimeter of the gull colony. In both years, 23-38% of parents, mostly males, showed "aggressive" defense behavior (strikes or chases) against crows and decoys. Other "non-aggressive" gulls showed no defense. In the year of low predation risk, intrusion rates by crows (landing within 0.5 m of an individual gull&apos;s nest) were similar for aggressive and non-aggressive gulls. In the year of high predation risk, however, the rates of intrusion for aggressive gulls (4%) and for non-aggressive gulls with an aggressive neighbor (37%) were significantly lower than for non-aggressive gulls without an aggressive neighbor (76%). These results indicate that aggressive individuals reduce nest predation risk for themselves and conspecific neighbors in a colonially breeding species.

Since parent birds are hypothesized to adjust the level of their nest defense against predators so as to enhance the survival of their offspring, parental nest defense is expected to increase in intensity in relation to increasing clutch size. Empirical studies of bird species, in which clutch sizes have been manipulated artificially, however, have produced results contradicting such expectations, partly, it is thought, because of various errors in experimental design, such as a lack of nesting habitat control, or providing too short a time for parents to assess the value of the manipulated clutch. Hence, further evidence needed to be gathered to clarify whether the basic hypothesis is adequately supported. We manipulated the clutch size of Black-tailed Gulls Larus crassirostris and observed the responses of male parents to a crow decoy in controlled nesting habitats. The intensity of defense was not affected by the clutch size. Opportunities for future reproduction, or constant individual levels of aggressiveness of seem to best explain the observed intensity of nest defense in these long-lived Black-tailed Gulls, rather than the value of the current clutch.

海洋資源を持続的に利用するためには，生態系を考慮したマネジメントが必須である．そのためには，生態系を構成する各要素について膨大な情報を収集し統合しなければならない．しかし，それはかなり困難であるので，効果的な生態系変化のインジケーターを使うことが重要である．海鳥は気候変化にともなう海洋生態系変動，および海洋環境汚染の便利なインジケーターであると信じられている．本論文では，1) 気候変化による海洋生態系変動に対する海鳥の反応，2) 海岸に漂着した海鳥の海洋油汚染インジケーターとしての有効性と海洋汚染の海鳥に対する潜在的インパクト，3) アホウドリ類の現状と保全，特に延縄による混獲についてレビューする．さらに，4) 世界における海鳥モニタリング活動と我が国における海鳥モニタリングの現状について紹介する．最後に，海鳥保全ネットワークの形成に関する提案をする．

高密度なコロニーを形成して繁殖するカモメ類では，捕食者からの逃避，他巣の親による攻撃，近接巣の給餌物に引き寄せられることなどによって生まれの巣から他の巣へと雛が移動し，移動先の巣の親に受け入れられ，給餌を受けたり保護を受けたりしてそのまま育てられることがある．本研究では，北海道利尻島で繁殖するウミネコについて，他巣の雛を追加して雛数を増加させた条件下で，他巣雛の受け入れ頻度に雛の日齢がどう関係するのかを実験的に調べた．1～3日齢の雛を付加した場合，7羽のうち6羽の雛が受け入れられたのに対し，8～10日齢の雛を付加した場合は，10羽のうち8羽の雛が拒絶された．これらのことは，ウミネコの親鳥が他巣雛を受け入れるかどうかは雛数の変動ではなく雛の日齢に依存することを示唆している．

近年，個体の老化や寿命との関係を示唆されているテロメアを用い， 長寿の鳥ウミネコLarus crassirostrisのテロメア齢推定の可能性を調べるために，雛時すなわち初期のテロメア長と成鳥におけるテロメア長を調査した．捕獲した成鳥（青森県蕪島個体）より採血しDNA抽出しテロメアを検出，計測した．同様に捕獲した雛（北海道利尻島個体）も行った．全年齢での回帰分析の結果，減少傾向にあることが分かった．しかし，雛においても成鳥においてもテロメア長の個体差が大きく，齢推定は困難であることが示唆された．

In some avian species, male plasma testosterone levels are maximum during the courtship or copulation periods, but decline abruptly once incubation starts. However, testosterone levels of male Black-tailed Gulls Larus crassirostris during the course of breeding remain unknown. In 2006, blood samples of 23 incubating males were collected at Rishiri Island, Hokkaido, Japan and testosterone was measured by enzyme immunoassay kit. Plasma testosterone level (mean&plusmn;S.E.: 0.737&plusmn;0.282 ng/ml) was assumed to decline with elapsed days from the onset of incubation, as shown in other species.

In colonial seabirds, nesting density, egg-laying date and nest microhabitat affect the probability of eggs being taken by avian predators. Jungle Crows (Corvus macrorhynchos) are dominant predators of eggs of Black-tailed Gulls (Larus crassirostris). Factors affecting the probability of gulls allowing the crows to attack their nests or depredate their eggs and the probability of eggs being taken were studied by direct observation and egg census, respectively. The effect of vegetation heights, position in the colony, egg-laying date and neighbour nests on the probability of eggs being taken were examined at multiple spatial scales. Gull nests were depredated more easily by larger groups of crows. Nests in peripheral areas (&lt; 4 m from the edge of the colony) were also depredated more easily by the crows walking on the ground. Although the nests where eggs were laid early in the season were depredated more frequently, such nests highly synchronised in egg laying within a &lt; 2-m radius were less likely to be depredated than less-synchronised nests. The nests in tall vegetation were less likely to be depredated though those having neighbour nests in tall vegetation were not. The number of neighbour nests did not affect the probability of eggs being taken. Antipredation effects of nesting microhabitats vary with spatial scales at which the crows search and attack the nests of gulls.

集団繁殖する海鳥の営巣数および繁殖個体数はこれまで2 次元面積を用いて推定されることが一般的であった．起伏に富む繁殖地に営巣する海鳥種や個体群では，この方法では巣の分布面積が過少評価され，推定数が実態より少なく見積もられることが懸念される．本報告は岩手県三貫島で実地調査したオオミズナギドリの植生タイプ別の巣数と繁殖個体数を，地理情報システム(GIS) を用いて標高を反映した3 次元面積で求め，2 次元面積で算出した結果と比較した．その結果，3 次元で求めた植生帯面積は2 次元で求めた面積の1.3倍になり，三貫島の地形，植生，地質条件下において，3 次元面積法による総推定巣数は，2 次元面積法の1.2 倍となった．3 次元面積法で得られた三貫島のオオミズナギドリ繁殖個体群の規模は，巣穴数約101,000 巣，巣立ち雛（巣数）約41,000羽（巣），および孵化時の繁殖個体数は約109,000羽と推定された．三陸沿岸の島嶼では，同所繁殖する小型ウミツバメ類がオオミズナギドリの営巣活動で減少する事例が指摘されており，三陸沿岸でオオミズナギドリが最も多く繁殖する三貫島でもウミツバメ類（特に絶滅危惧種ヒメクロウミツバメ）に対する競争排除が憂慮された．