Deaths of Birds and Mammals from Toxic Chemicals September 1961-August 1962.

Abstract

1. Between September, 1961, and August, 1962, 119 incidents of mortality alleged to be due to toxic agricultural chemicals were reported to the Joint Committee of the Royal Society for the Protection of Birds and the British Trust for Ornithology, and the Game Research Association. Although this is a decrease from the 324 incidents reported in the first six months of 1961, the number of incidents alleged to be due to sprays or horticultural pesticides has increased. slightly.
2. Ninety-seven chemical analyses were made of 122 bodies of birds by an independent analyst. All except five contained mercury or organo-chlorine compounds. Tests were not as a rule made for other chemicals. There was, in general, a marked reduction in the proportion of mercury and organo-chlorine compounds found in the specimens examined compared with 1961.
3. Of the 67 specimens submitted to a more detailed examination to identify the specific chemicals involved, 51 contained dieldrin, 15 heptachlor epoxide, 13 benzene hexachloride and 10 aldrin. D.D.T. was found in substantial quantities in a Song Thrush. Bodies of nocturnal and diurnal birds of prey were found 'to contain mercury and one or more organo-chlorine pesticide.
4. Residues of organo-chlorine compounds were found in the deserted eggs of Pheasants. This new and disquieting feature may indicate the effects on fertility of a sub-lethal dose of pesticides. Reduced breeding success of Pheasants and Red-legged Partridges is also reported, as well as the poisoning of fledgling House Martins and Swallows.
5. Although residues from organo-chlorine pesticides are small, a new method of analysis showed that some bodies contained as many as four different compounds. It appears that a fairly high proportion of the bird population is already carrying a sub-lethal dose of poison.
6. Deaths resulting from the use of pesticides were reported in most months. Bird deaths from seed dressings were heaviest in October and November, 1961, and from March to May, 1962. Deaths resulting from sprays and other applications of insecticides tended to follow seed dressing deaths and occurred as late as August.
7. Deaths from seed dressings were recorded from 23 counties and 26 species of birds, compared with 50 species from 44 counties in 1961. Pheasants, Woodpigeons, Partridges and Greenfinches were the most commonly recorded casualties, but increased numbers of birds of prey were found dead.
8. According to the records of the Joint Committee, the number of deaths reported in seed dressings incidents has declined, but the Game Research Association reports that the scale on which deaths have occurred is similar to 1961.
9. Five cases have been brought to our notice in which the voluntarily banned compounds-aldrin, dieldrin and heptachlor-were used in spring, and caused deaths.
10. The effect of sprays and garden insecticides has increased slightly compared with 1961, and a total of forty incidents is reported from 19 counties, with Kent the most heavily affected.
11. In the cases of a number of single dead birds the source of the poison was difficult to establish and in some instances the poison apparently came from a number of sources.
12. The report concludes by calling for the maintenance and extension of fundamental and applied research recommended by the Sanders Committee. It welcomes the study on residues in predatory birds which is being made by the Nature Conservancy. It asks that more selective chemical compounds should be developed and, finally, emphasises the need for the vigilance of the countryman, the amateur observer, and the voluntary societies.