読み方
実測 ― 衛星追跡の記録に基づくもの/文献値 ― 公開資料に記された数値や時期/模式 ― 公開文献をもとに再構成した概略の経路で、追跡軌跡そのものではありません/演出 ― 季節の光、雲の影、係留地の風景など、体験のための表現です。海岸線は Natural Earth の実データに、地形の陰影は実標高データ(AWS Terrain Tiles/Mapzen ― SRTM・GMTED2010等)から作成した陰影図に基づきます。
ナベヅル
時期・個体数は日本野鳥の会・環境省等の公開資料に基づく文献値。経路は模式。世界の推定個体数は約16,000羽(IUCNレッドリスト 絶滅危惧II類 VU)。出水には例年約1万〜1万3千羽 ― 世界の約8〜9割 ― が飛来し、滞在中は約75トンの小麦などが給餌されます。
ツバメ
日本の夏鳥。繁殖・越冬の時期と生態は日本野鳥の会等の公開資料に基づく文献値。越冬地は東南アジア一帯(一部はオーストラリア北部)。経路は代表的な一群の模式で、距離約4,300kmは概算です。
ハチクマ
春と秋で異なるルート、東シナ海700km超の横断、片道約10,000kmは、衛星追跡研究(樋口広芳ら)による実測・文献値。二つの経路の線は、その知見をもとに再構成した模式です。
オオジシギ
約6,000km・7日間の無着陸飛行は、2016年に衛星追跡された個体の記録(日本鳥学会誌等)による実測。北帰行は実際には太平洋の島々を経由するとされますが、ここでは一本の線に模式化しています。
キョクアジサシ
年間移動距離 平均約70,900km、一生で約240万kmという推定は、Egevang et al. 2010(PNAS)の追跡研究に基づく文献値で、大西洋の個体群についての値です。この図の太平洋側の経路は模式です。
サシバ
樋口広芳らによる衛星追跡4羽の研究(環境省研究報告)と、日本鳥類保護連盟のGPS追跡プロジェクトに基づく文献値・実測。経路は模式。秋のピークは9月下旬〜10月です。
マガン
伊豆沼・宮島沼の研究蓄積(嶋田哲郎ら)とGPS追跡に基づく文献値。東シベリアの繁殖地との往復と中継地が解明されています。伊豆沼周辺の越冬数は約10万羽(文献値)。
オオハクチョウ/コハクチョウ
SwanEyesプロジェクト(2023年12月〜、伊豆沼・内沼環境保全財団)のカメラ付きGPS首輪による実測。愛称個体(ミホ、アキラ、ヒトシ等)の位置と画像が公開されています。コハクチョウの個体ニジカの2025年秋の軌跡(10月3日シベリア発、14日瓢湖着)は観察記録の詳報に基づきます。
ヘラシギ
衛星タグ15羽の追跡に基づく実測。2016年に江蘇省条子泥でタグを付けられたETは、インドシナを陸路横断してミャンマー・モッタマ湾へ達しました。世界の個体数は800羽未満(CR)。BirdLifeの文献自身が「繁殖地の4分の3、越冬地の半分はまだ分からない」と明記しており、この作品でも未知は未知として描きます。
クロツラヘラサギ
GPS追跡39羽超の黄海横断データ(学術論文)に基づく実測。個体M03は2021年11月7日に韓国を発ち、502kmを10.5時間で渡ったのち、洋上風力発電所に遭遇して進路を変え、引き返した記録が残ります。最大の越冬地は台湾・曽文渓口です。
シジュウカラガン
1962/63年のアリューシャンでの再発見、千島・エカルマ島への551羽の放鳥(1995〜2010年、仙台市八木山動物公園ほか)、宮城県への飛来数の回復(2021年度8,000羽超)は、仙台市・日本雁を保護する会等の記録に基づく文献値。主人公は特定の個体ではなく「放鳥世代の子孫」という再構成で、その枠組みを明示しています。
アマツバメ
サハリンで繁殖する3個体のジオロケータ通年データ(学術論文)に基づく実測。南下は平均約9,000km、大陸への迂回は直線比で約30%長く、中継は4〜44日。「寝ながら飛ぶ」といった未検証の誇張は用いていません。
マナヅル
樋口らの衛星追跡5羽(Conservation Biology 1996ほか)が、最短でない湿地の多い経路と、朝鮮半島DMZ・鉄原の重要性を実証しました。2025年に出水でGPSを装着された個体には、地元の子どもたちにより「イズリア」と命名され、経路公開プロジェクトが進行中です。出水と鄱陽湖は別個体群の越冬地です。
オオソリハシシギ
衛星追跡の実測。E7(2007年、11,680km無着陸、往復29,280km)、4BBRW(2020年12,200km、2021年13,050km)、幼鳥B6(2022年、13,560kmを11日1時間無着陸、アラスカからタスマニア、タグ番号234684)。北上は黄海経由、南下は太平洋直行。日本には旅鳥として少数が立ち寄ります。
ホウロクシギ
ジオロケータ個体EC07、EC23、EC24(ビクトリア州)の記録 ― 8,500km無着陸で黄海へ、約3週間の中継ののちアムールへ ― と、衛星追跡21羽のデータセット(2017〜2020年)に基づく実測・文献値。世界最大のシギです。
オバシギ
Australasian Wader Study Groupの標識・追跡の蓄積に基づく文献値。南下ではオホーツク海からオーストラリア北部へ約8,000kmを直行する個体が多く、北上では鴨緑江・黄海が要の中継地です。
アホウドリ
日米共同衛星追跡19個体(環境省・山階鳥類研究所)に基づく実測。個体数は1949年に絶滅と言われ、1951年に約10羽で再発見、2026年に推定11,067羽(山階鳥研発表)。季節移動は「繁殖地と非繁殖期の海域の往復」として描いています。
オオミズナギドリ
冠島のジオロケータ研究(山本誉士ら)で越冬海域が判明し、粟島のGPS研究で幼鳥の山越え南下が記録されています。最長寿の標識記録は1975年に冠島で標識、2012年にマレーシア・ラブアン島で確認(標識後36年8か月、推定40歳超、3,964km)。主人公はその個体を核にした再構成で、明示しています。
ハシボソミズナギドリ
ジオロケータによる通年の渡りの初記載(Great Dog島、タスマニア)に基づく実測。南極前線での中継、日本近海とベーリング海での夏、中央太平洋を南下する8の字の経路。片道約15,000km、約200日。
オオワシ
衛星追跡(Ueta et al. 2000、McGrady et al. 2003)と放鳥追跡(環境省検討会資料)に基づく実測。流氷に乗る移動、宗谷からサハリンへの2時間の横断が記録されています。個体数は推定5,000〜7,000羽。
ノスリ
衛星追跡17〜22羽(Yamaguchi et al., Zoological Science 2022)とGPS追跡28羽に基づく実測。日本海を境とする亜種間の「渡りの分断」が示されています。
コウノトリ(条件付き収録)
大陸の野生個体群は衛星追跡のある真の渡り鳥(アムール・ウスリー繁殖、長江流域・鄱陽湖越冬)で、日本の番号個体の韓国への渡航記録(2014年〜)と野生個体ハチゴロウの飛来(2002年)も実在します。この二つを出典つきで構成できるため、「帰ってきた渡り鳥」として収録しました。日本の再導入個体の多くは分散型であることも、作中で明示しています。
オオルリ(条件付き収録)
ジオロケータ1個体の実記録(ロシア極東で繁殖、台湾・中国沿岸・朝鮮半島経由、フィリピン・ミンドロ島で5か月)に基づきます。「大陸で繁殖する一羽の実記録」として枠組みし、日本の繁殖個体の経路は未解明であることを明示して収録しました。
収録しなかった鳥
ムナグロは、日本に実際に来る追跡個体を出典つきで示すことが今回できませんでした。ブッポウソウ、サンコウチョウ、カッコウ、ミサゴは、日本の個体群を追った確かな記録が不足するため、収録していません。根拠の足りない鳥は、描かないことにしています。
新しい図の地形について
拡張した5つの図の海岸線は Natural Earth(50m)の実データから、地形の陰影は既存の図と同基準で、実標高データ(AWS Terrain Tiles ― SRTM・GMTED2010等)から作成した陰影図に基づきます。同じ図を共有する鳥たちは、同じ空に同時に描かれます。
旅の主役について
ナベヅルの家族、ツバメ、キョクアジサシの主役は、公開文献に基づく再構成です。ハチクマの主役は衛星追跡研究に記録された振る舞いに、オオジシギの主役は2016年に実際に衛星追跡された実在の個体に基づきます。いずれも、創作の会話や性格付けは加えていません。
今日の空・番外編について
「今日の空」は実況データではなく、文献値と例年の目安に基づく季節の目安です。経路の外の発見(番外編)も、公開資料に基づく文献値です。キョクアジサシの航跡の重なりは、年を重ねた分だけ残る演出で、その位置は模式です。
同行モードの景観について
群れが降りた土地の景観は演出ですが、三つのことだけは実際に合わせています。遠くの山並みは、その土地の実在の地点(出水なら荒崎付近、伊豆沼、瓢湖、羅臼、鳥島の沖など)から見た実際の稜線を、実標高データ(AWS Terrain Tiles)から計算して描いています(高さの誇張なし)。太陽は、その日・その時刻に実際にある方角と高さに置いています。そしてそこにいる鳥は、その土地に実際にいる種で、距離に応じた大きさで描いています。水田や湿原、干潟、森の描き方そのものは絵です。
写真について
「この鳥」と旅の主役の欄の写真は、Wikimedia Commons と iNaturalist で自由な利用が認められた写真です(パブリックドメイン/CC0、または撮影者の表示を条件とする CC BY)。同じ種の別の個体を写したもので、旅の主役の個体ではありません。いずれも 3:2 にトリミングし、縮小して掲載しています。
How to read this
Measured — based on satellite-tracking records / Published figure — numbers and timings stated in published sources / Schematic — an approximate route reconstructed from the published literature, not the tracked trajectory itself / Artistic rendering — expression for the sake of the experience, such as seasonal light, cloud shadows and the scenery of the places where the birds rest. The coastlines are based on real data from Natural Earth, and the terrain shading on hillshade images made from real elevation data (AWS Terrain Tiles / Mapzen — SRTM, GMTED2010 and others).
Hooded Crane
Timing and numbers are published figures from public sources of the Wild Bird Society of Japan, the Ministry of the Environment and others. The route is schematic. The estimated world population is about 16,000 (IUCN Red List: Vulnerable, VU). Every year about 10,000–13,000 birds — some 80–90% of the world’s total — come to Izumi, where about 75 tonnes of wheat and other food are provided during their stay.
Barn Swallow
A summer visitor to Japan. The timing of breeding and wintering, and its ecology, are published figures from public sources of the Wild Bird Society of Japan and others. It winters across Southeast Asia (some as far as northern Australia). The route is a schematic of one representative group, and the distance of about 4,300 km is an estimate.
Oriental Honey Buzzard
The different routes in spring and autumn, the crossing of more than 700 km of the East China Sea, and the one-way distance of about 10,000 km are measured and published figures from satellite-tracking research (Hiroyoshi Higuchi and colleagues). The two route lines are a schematic reconstructed from those findings.
Latham’s Snipe
The nonstop flight of about 6,000 km in seven days is measured, from the record of a bird satellite-tracked in 2016 (Japanese Journal of Ornithology and others). The journey north is in fact thought to pass by islands in the Pacific, but here it is simplified into a single line.
Arctic Tern
The estimates of an average of about 70,900 km travelled each year and about 2.4 million km in a lifetime are published figures from the tracking study of Egevang et al. 2010 (PNAS), and refer to the Atlantic population. The Pacific route on this map is schematic.
Grey-faced Buzzard
Published and measured figures from the satellite tracking of four birds by Hiroyoshi Higuchi and colleagues (a Ministry of the Environment research report) and from the GPS-tracking project of the Japanese Society for Preservation of Birds. The route is schematic. The autumn peak is from late September into October.
Greater White-fronted Goose
Published figures from the long body of research at Izunuma and Miyajimanuma (Tetsuo Shimada and colleagues) and from GPS tracking, which have revealed the round trip to and from the breeding grounds in eastern Siberia and the stopovers along the way. About 100,000 birds winter around Izunuma (published figure).
Whooper Swan / Tundra Swan
Measured, by the camera-equipped GPS collars of the SwanEyes project (since December 2023, Izunuma-Uchinuma Environmental Foundation). The positions and images of the named birds (Miho, Akira, Hitoshi and others) are made public. The autumn 2025 track of the Tundra Swan Nijika (left Siberia on 3 October, arrived at Hyoko on the 14th) is based on a detailed report of the observation records.
Spoon-billed Sandpiper
Measured, from the tracking of 15 satellite-tagged birds. ET, tagged at Tiaozini in Jiangsu in 2016, crossed Indochina overland to reach the Gulf of Mottama in Myanmar. Fewer than 800 remain in the world (Critically Endangered, CR). BirdLife’s own literature states plainly that ‘three quarters of the breeding grounds and half of the wintering grounds are still unknown’, and in this work, too, the unknown is drawn as unknown.
Black-faced Spoonbill
Measured, from Yellow Sea crossing data on more than 39 GPS-tracked birds (academic papers). The bird M03 left Korea on 7 November 2021 and crossed 502 km in 10.5 hours; the record shows him then meeting an offshore wind farm, changing course and turning back. The largest wintering ground is the Zengwen estuary in Taiwan.
Aleutian Cackling Goose
The rediscovery in the Aleutians in 1962/63, the release of 551 birds on Ekarma in the Kuril Islands (1995–2010; Sendai Yagiyama Zoological Park and others), and the recovery of arrivals in Miyagi Prefecture (more than 8,000 in fiscal 2021) are published figures from the records of the City of Sendai, the Japanese Association for Wild Geese Protection and others. The protagonist is not a particular bird but a reconstruction — ‘the descendants of the released generations’ — and that framing is stated plainly.
Pacific Swift
Measured, from year-round geolocator data on three birds breeding on Sakhalin (an academic paper). The journey south averaged about 9,000 km, the detour around the continent was about 30% longer than a straight line, and the stopovers lasted 4 to 44 days. Unverified exaggerations such as ‘it sleeps on the wing’ are not used.
White-naped Crane
The satellite tracking of five birds by Higuchi and colleagues (Conservation Biology 1996 and others) showed that they take a route rich in wetlands rather than the shortest one, and demonstrated the importance of the DMZ and Cheorwon on the Korean Peninsula. A bird fitted with GPS at Izumi in 2025 was named ‘Izuria’ by local children, and a project publishing its route is under way. Izumi and Poyang Lake are the wintering grounds of separate populations.
Bar-tailed Godwit
Measured, by satellite tracking: E7 (2007; 11,680 km nonstop, 29,280 km for the round trip), 4BBRW (12,200 km in 2020, 13,050 km in 2021) and the juvenile B6 (2022; 13,560 km nonstop in 11 days 1 hour, from Alaska to Tasmania, tag number 234684). The journey north goes by way of the Yellow Sea; the journey south is nonstop across the Pacific. Small numbers stop in Japan as passage migrants.
Far Eastern Curlew
Measured and published figures from the records of the geolocator birds EC07, EC23 and EC24 (Victoria) — 8,500 km nonstop to the Yellow Sea, then on to the Amur after a stopover of about three weeks — and from a dataset of 21 satellite-tracked birds (2017–2020). It is the world’s largest sandpiper.
Great Knot
Published figures from the accumulated banding and tracking of the Australasian Wader Study Group. On the journey south many birds fly about 8,000 km nonstop from the Sea of Okhotsk to northern Australia; on the journey north the Yalu River and the Yellow Sea are the key stopovers.
Short-tailed Albatross
Measured, from 19 birds satellite-tracked in a joint Japan–US study (Ministry of the Environment, Yamashina Institute for Ornithology). The species was said to be extinct in 1949, was rediscovered with about ten birds in 1951, and was estimated at 11,067 birds in 2026 (announced by the Yamashina Institute). Its seasonal movement is drawn as ‘a round trip between the breeding ground and the seas of the non-breeding season’.
Streaked Shearwater
Geolocator research on Kanmuri-jima (Takashi Yamamoto and colleagues) revealed its wintering waters, and GPS research on Awashima recorded fledglings flying south over the mountains. The longest-lived banding record is a bird banded on Kanmuri-jima in 1975 and found on Labuan, Malaysia, in 2012 (36 years 8 months after banding, estimated to be over 40 years old, 3,964 km away). The protagonist is a reconstruction built around that bird, and this is stated plainly.
Short-tailed Shearwater
Measured, from the first description of its year-round migration by geolocator (Great Dog Island, Tasmania): a figure-of-eight route with a stopover at the Antarctic Front, summer in the seas around Japan and in the Bering Sea, and the return south through the central Pacific. About 15,000 km and about 200 days each way.
Steller’s Sea Eagle
Measured, from satellite tracking (Ueta et al. 2000; McGrady et al. 2003) and release tracking (documents of a Ministry of the Environment study group). Movements riding the drift ice, and a two-hour crossing from Soya to Sakhalin, have been recorded. The population is estimated at 5,000–7,000.
Eastern Buzzard
Measured, from the satellite tracking of 17–22 birds (Yamaguchi et al., Zoological Science 2022) and the GPS tracking of 28 birds. They show a ‘migratory divide’ between subspecies, with the Sea of Japan as its boundary.
Oriental Stork (included on conditions)
The wild continental population is a true migrant with satellite-tracking records (breeding along the Amur and Ussuri, wintering in the Yangtze basin and at Poyang Lake), and the records of numbered birds from Japan crossing to Korea (from 2014) and the arrival of the wild bird Hachigoro (2002) are real as well. Because these two could be put together with their sources, the species is included as ‘the migrant that came back’. That most of Japan’s reintroduced birds disperse rather than migrate is also stated plainly in the work.
Blue-and-white Flycatcher (included on conditions)
Based on the actual record of a single geolocator bird (breeding in the Russian Far East; by way of Taiwan, the Chinese coast and the Korean Peninsula; five months on Mindoro in the Philippines). It is included under the framing ‘the actual record of one bird that breeds on the continent’, with a plain statement that the route of birds breeding in Japan has not been worked out.
Birds not included
For the Pacific Golden Plover, we could not this time show, with sources, tracked birds that actually come to Japan. The Oriental Dollarbird, Japanese Paradise Flycatcher, Common Cuckoo and Osprey are not included because reliable records following their populations in Japan are lacking. Birds without enough evidence, we have chosen not to draw.
The terrain of the new maps
The coastlines of the five added maps come from real Natural Earth data (50m), and their terrain shading, on the same basis as the existing maps, from hillshade images made from real elevation data (AWS Terrain Tiles — SRTM, GMTED2010 and others). Birds that share a map are drawn in the same sky at the same time.
The protagonists
The protagonists of the Hooded Crane family, the Barn Swallow and the Arctic Tern are reconstructions based on the published literature. The Oriental Honey Buzzard’s protagonist is based on behaviour recorded in satellite-tracking research, and Latham’s Snipe’s on a real bird that was actually satellite-tracked in 2016. In no case have invented dialogue or personalities been added.
Today’s sky and the extras
‘Today’s sky’ is not live data but a seasonal guide based on published figures and typical timing. The discoveries off the route (the extras) are also published figures from public sources. The layering of the Arctic Tern’s tracks is an artistic rendering that remains for each year lived through, and its position is schematic.
The scenery when you join the flock
The scenery of the places where the flock comes down is an artistic rendering, but three things alone are matched to reality. The distant mountains are the real skylines seen from actual points in each place (near Arasaki for Izumi; Izunuma, Hyoko, Rausu, off Torishima and others), computed from real elevation data (AWS Terrain Tiles) and drawn without exaggerating their height. The sun is placed in the direction and at the height where it really is on that day, at that hour. And the birds there are species actually found in that place, drawn at sizes that match their distance. The rice fields, marshes, mudflats and forests themselves are painted.
The photographs
The photographs in ‘This bird’ and in the protagonist panel are ones whose free use is permitted on Wikimedia Commons and iNaturalist (public domain / CC0, or CC BY, which requires crediting the photographer). They show other birds of the same species, not the protagonists themselves. Each has been cropped to 3:2 and reduced in size.