要 約
１．全国47都道府県（島嶼部は原則として除く）を対象として、日本で繁殖する又は繁殖の可能性のある257種（外来種13種を含む）の鳥の繁殖分布調査が、環境庁の委託により日本野鳥の会によって1978年度に実施された。
２．国土地理院発行の２万５千分の１地形図を４分割したサブメッシュを調査区画単位とし、現地調査と資料調査を行って、生息鳥類の種類と繁殖の可能性、生息環境の概要、および個体数の概況等を記録した。
３．現地調査は986人の調査員により全国4,371区画のうち2,225サブメッシュに於て実施された。資料調査を加えて得られた結果は、次の通りである。繁殖を確認した（Ａランク）種類は、188種、繁殖の確認は出来なかったが、その可能性があるもの（Ｂランク）は11種、生息を確認したが繁殖については何ともいえないもの（Ｃランク）は６種となり、合計205種（調査対象種の79.8％）であった。
４．繁殖に関しての肯定的な結果の得られなかったＤ、Ｅ、Ｆランクの52種（調査対象種の20.2％）については、繁殖分布図は省かれている。しかし、これらの中には調査メッシュ以外で繁殖している、又はその可能性の強いと思われる種類（イヌワシ、タンチョウ、フクロウなど）や、繁殖はすでに確認されているものの、局地的に生息する為今回の調査で結果の得られなかった種類（アホウドリ、アカコッコ、メグロなど）が含まれている。従って、Ｄ〜Ｆランクの総ての種類が直ちに稀少種や絶滅しそうな種であることを意味してはいない。
５．調査対象種以外では、セグロカッコウ（Ｂランク）とアメリカオシドリ（Ａランク）が報告された。
６．調査の最終結果である繁殖状況票と環境調査票のすべてのデータは磁気テープ化され、電算機により繁殖分布図の作製および集計が行なわれた。
７．本報告書の205種の分布地図は鳥類コードの順に配列されている。各区画は、国土地理院発行の５万分の１地形図に相当し、その範囲に含まれる調査結果のランクの最も高いものをとって表示した。大中小の黒丸は、それぞれＡ、ＢおよびＣランクを示す。
８．サブメッシュ単位でのランク別の全国集計結果は、各種毎の解説の末尾に加えた。
９．本報告書に掲載された全国繁殖分布地図は、1978年度の現地調査および1974−78年の間の繁殖記録を集めた資料調査の結果だけをもとに作製された。従って、調査の実施されなかった地域（特に島嶼部）や、調査期間以前の記録などは、地図化の対象となっていない。今後の調査により分布地図の内容が一層充実されねばならぬことは言う迄もない。尚、この繁殖地図調査は今後略５年に一度実施される予定である。
SUMMARY
The nation-wide breeding bird survey, contracted by the Japan Environmental Agency, was conducted by the Wild Bird Society of Japan in 1978. All 47 provinces were covered except some remote islands. Included in the count were 257 species of birds including 13 exotic ones which are conceivably or certainly known to breed in Japan.
The field survey took place in 2,225 survey units, each unit covering a 1/4 section of the 1/25,000 topography maps published by the Geographical Survey, Institute of Ministry of Construction. They were selected at random within areas of greater variety of bird life, and counts were made by 986 obserbers in the following manner: Thirty minute stop counts were made at the beginning and end of each route interspersed with a roadside count while walking from one end of the route to the other. All birds seen or heard were counted and recorded by species along with any bird behavior particularly associated with breeding and brief descriptions of the habitats along the route. Since the primary aim of this survey is to map the breeding range for each species recorded, emphasis was placed on the collection of breeding data. The data obtained in the field in 1978 were supplemented by a literature survey collecting as much breeding data as possible for the 1974-78 period.
Recorded as A, B, or C rank in the survey were 205 species, of which 188 species are confirmed breeders (A rank), 11 are probable breeders (B rank), and ６ are possible breeders (C rank). An additional 27 species are possibly non-breeders (D rank) and nothing was reported on 25 species (E and F ranks) out of possible 257 species. A part of this reason lies in the fact that no field survey was conducted due to inaccessibility despite the known breeding habitat. Of the 205 species counted, 14 are classed as special species requiring strict protection. In addition to the 205 species, the Indian Cuckoo Cuculus and American Wood Duck Aix sponsa were reported as probable and confirmed breeder respectively. Their status as regular breeders in Japan seems debatable.
All field data were transferred to magnetic tape for computer tabulation and range map production. The range maps consist of overlay quadrants which represent the Geographical Survey maps, scale 1/50,000, encompassing 16 of the survey units. The breeding rank given for each species found in a given quadrant was assigned on the basis of the observed behavior and the reports in the literature covering that quadrant. The highest ranking found in any of the data sources was assigned to each species in the quadrant. The highest rank thus selected is marked on the map by large, medium or small dot denoting A, B, or C rank respectively. An A rank means that breeding is confirmed by one or more facts directly associated with breeding activities; B rank, the breeding is not confirmed but probable because of observed activities related to breeding; and C rank, birds are recognized during breeding season in possible nesting habitat, but there is no judgement made as to breeding. A quadrant with no dot means that the field survey in at least two survey units and/or the literature survey in certain units were actually conducted but no evidence for A, B, or C ranking was recorded.
In this report, all 205 breeding maps are arranged according to the ornithological code as used in the 5th edition of the Check-List of Japanese Birds. The nation-wide result of the breeding rank is tabulated by survey units at the end of each species account.
Since the scope of the data collected for these maps covers only the last 5 years, obviously more data must be gathered and upgraded to obtain breeding distribution maps which reflect more precisely the actual field condition. Therefore, this survey is to be conducted in every 5 years starting in 1978.