Mercury in feathers of wild birds from the mercury-polluted area along the shore of the Shiranui Sea, Japan.

Abstract

Total mercury content in the feathers of 95 stuffed, wild birds collected all over the shore of the Shiranui Sea (where Minamata disease occurred in many towns and villages in the 1960's) was measured. They were collected over 25 years, from 1955 to 1980. They showed relatively high mercury levels till the late 1970's, although drainage of waste water containing methylmercury from the Chisso Corporation's Minamata Factory was stopped in 1968. In addition, a strong correlation between feeding habits and mercury content was observed; thus the five groups in order of diminishing mercury content were: fish-eating sea birds (mean +/- SD = 7.1 +/- 3.7 ppm, n = 14), omnivorous water fowl (5.5 +/- 5.6 ppm, n = 17), predatory birds (3.6 +/- 2.9 ppm, n = 16), omnivorous terrestrial birds (1.5 +/- 1.2 ppm, n = 31), and herbivorous water fowl (0.9 +/- 0.4 ppm, n = 17). Mercury content of the feathers of omnivorous terrestrial birds in the Shiranui Sea was exceedingly high compared with those in China and Korea. The findings in the present study suggest that stuffed, wild birds may be a good index of past environmental pollution.