DDD and DDE were fed separately to groups of cowbirds (Molothrus ater). Residues in brains of birds killed by the chemicals were distinctly higher than in brains of birds sacrificed after similar exposure, thus providing criteria for assessing cause of death and judging residue levels in field specimens. Residues in liver and carcass appeared unsuitable for diagnosing cause of death. Brain residues of DDD at death were estimated to be 65 ppm (wet weight) or higher in 95 percent of the cases with an average of 172 ppm. Residues of DDE in the brain at death were estimated to be 314 ppm or higher in 95 percent of the cases with an average of 4 99 ppm. Tentative suggestions axe made for weighting and summing brain residues of DDT, DDD, and DDE for interpretation of field specimens. DDD was approximately twice as toxic as DDE. Survival time on dosage was directly related to pretreatment weight; the heaviest birds rhed last but retained the greatest proportion of body fat. Gross effects seen at necropsy differed between birds fed DDD and those fed DDE.
Additional publication details
DDE and DDD residues correlated with mortality of experimental birds