ORGANOCHLORINE RESIDUES AND MORTALITY OF HERONS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 14  (4) , 125-135
Abstract
Since 1966, 72 herons found dead or moribund in the field were analyzed for organochlorine chemicals. In addition, 36 herons were obtained through systematic collections and carcasses were analyzed to determine sublethal exposure to organochlorines. Brains of birds found dead or moribund were analyzed to determine whether the birds had died of organochlorine poisoning. Residues of DDE were found most frequently (96 of 105 carcasses analyzed), PCB [polychlorinated biphenyl] were 2nd (detected in 90 carcasses) and dieldrin and DDD (detected in 37 and 35 carcasses, respectively) were about equal as 3rd and 4th most frequent. Endrin, mirex, toxaphene and BHC were found least often (8, 9, 9 and 9 carcasses, respectively). At least 1 organochlorine was found in each carcass, except for 6 heron chicks found dead in a Maryland [USA] heronry. DDE and PCB were present in highest concentrations; they exceeded 100 ppm in 2 birds each. Organochlorine concentrations were usually higher in adult herons than in immature birds. All birds that had hazardous or lethal concentrations in the brain were adults and most were great blue herons (Ardea herodias). Dieldrin was the chemical most often considered responsible for death. Herons died of suspected DDT and dieldrin poisoning years after the chemicals were banned in USA. More than 20% of the herons found dead or moribund had lethal or hazardous concentrations of organochlorines in the brain.