Effects of DDT on the Fish Eagle Haliaeetus vocifer population of Lake Kariba in Zimbabwe

摘要: Twenty clutches were collected from nests of Fish Eagles Haliaeetus vocifer at Lake Kariba, Zimbabwe, and a small dam nearby in 1989-90. Unaltered DDT, metabolites DDD DDE, found every egg. Mean levels σDDT(= DDT + DDE) generally varied 14 to 49 mg/kg dry weight per clutch, but 113–223 the eastern end lake mouth Sengwa River. SDDT DDE significantly correlated with Ratcliffe Index eggshell thickness. Comparison museum specimens showed that has declined by 11% since 1936-41 due significant fall shell weight. Eggshell thinning exceeded 20% lake. Aerial surveys 1987 1990 hatching success along southern lakeshore 72%, chicks seen fewer than half end. However, density breeding pairs was greatest here. Residue have increased about 8% 1980, rising more steeply areas recently sprayed for tsetse fly control falling others. The threat may now be receding as regional use will end, control, 1995. None used this purpose 1991. Mercury adult birds very high pose risk. The population limited availability safe nest sites. Chicks are sometimes eaten people. Settlement is increasing sites becoming scarcer dead trees collapse large onshore destroyed elephants.