An qenstionaeir survey of shearwater mortality

Abstract

1) The mortality of the Shearwaters in 1975, especially the Slenderbilled Shearwaters, were surveyed by the questionnaire method. The questionnaires were recovered from 263 persons (Recovery rate 13%), and more than 80% of them were from the members of Japan Wild Birds Society and Japanese Association for Preservation of Birds.2) The number of the dead shearwaters, according to the questionnaire of 1975, was approximately 19.768, the number of birds found in emaciated condition was 787, and the number found afloat was 14, 924. The recorded species were Slender-billed Shearwater Puffinus tenuirostris (account for 76, 2% of all dead and emaciated Shearwaters), Streaked Shearwater Calonectris leucomeas (account for 0.8%), Sooty Shearwater Puffinus griseus (account for 0.6%), Pale-footed Shearwater Puffinus carneipes and Wedged-tailed Shearwater Puffinus pacificus. (Among these, the species account for 22.4% of all the dead and emaciated birds were indistinct.)3) The dead Shearwaters were distributed in the districts along the Pacific Coast, from Kagoshima Prefecture to Hokkaido. The distribution of the dead Slender-billed Shearwaters that have the highest death rate cover 15 Prefectures from Kagoshima Prefecture to Hokkaido.4) According to the survey, most of the dead Slender-billed Shearwaters were recorded from the beginning of May to the beginning of July, and the time of great mortality seems to lag in the northern districts.Throughout the country, the times of highest shearwater mortality were from the beginning (56.2%) to the middle (26.2%) of June.5) Many of the people who have answered the questionnaires reported that the stomachs were empty when they dissected the dead shearwaters. However, few of them reported that such things as coal tar, sand, pebbles, piece of wood and styrofoam etc. were found in the stomach. According to the result of the dissection in 5 cases, there were no external wounds, and all were juveniles.6) It was reported that the shearwaters were found feeding in the corfs in some part of the districts.7) The mortality of the Slender-billed Shearwaters before 1975 has been recorded mainly in 1973 and 1974, and in 1962, 1964, 1969, 1970 and 1971, mortality was recorded only in one part of the district (City of Sendai). Especially, the record of 1964 accord with the report of Dr. Nagahisa Kuroda on the mortality of the Shearwaters (1967).Also, the record of 1964 showed that the dead Shearwaters were distributed as far north as the Tohoku District.8) The distribution of the dead Slender-billed Shearwaters in 1974 and 1975 further extended to Tohoku and Hokkaido compared with the record of the distribution of 1966 and 1973, and there seemed to be a tendency that the time of the mortality lag according to the extension of the distribution.